A review of possible toxicity of di-2-ethylhexylphthalate (DEHP) in plastic intravenous containers: effects on reproduction

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.

Endocrine disrupting chemicals (EDCs) and sex steroid receptors

Sex-steroid receptors (SSRs) are essential mediators of estrogen, progestin, and androgen signaling that are critical in vast aspects of human development and multi-organ homeostasis. Dysregulation of SSR function has been implicated in numerous pathologies including cancers, obesity, Type II diabetes mellitus, neuroendocrine disorders, cardiovascular disease, hyperlipidemia, male and female infertility, and other reproductive disorders. Endocrine disrupting chemicals (EDCs) modulate SSR function in a wide variety of cell and tissues. There exists strong experimental, clinical, and epidemiological evidence that engagement of EDCs with SSRs may disrupt endogenous hormone signaling leading to physiological abnormalities that may manifest in disease. In this chapter, we discuss the molecular mechanisms by which EDCs interact with estrogen, progestin, and androgen receptors and alter SSR functions in target cells. In addition, the pathological consequences of disruption of SSR action in reproductive and other organs by EDCs is described with an emphasis on underlying mechanisms of receptors dysfunction.

Lycium Barbarum Polysaccharides and Wolfberry Juice Prevent DEHP-Induced Hepatotoxicity via PXR-Regulated Detoxification Pathway

Environmental di(2-Ethylhexyl) phthalate (DEHP) is widely used in various industries as a plasticizer, and has been reported to induce reproductive and developmental toxicities in organisms. The purpose of this study was to evaluate the detoxification capacity of Lycium barbarum polysaccharides (LBP) and wolfberry juice (WJ) against DEHP-induced hepatotoxicity. Two groups of rats were purchased to study two different intervention method experiments: LBP (50, 100, 200 mg/kg·bw) intervention before DEHP (2000 mg/kg·bw) exposure, and LBP (200 mg/kg·bw) or WJ (8 mL/kg·bw) intervention after DEHP (3000 mg/kg·bw) exposure. The rats were exposed to DEHP once, while the intervention lasted for seven days. At the end of the intervention, enzyme-linked immunosorbent assay (ELISA) was used to measure the related index. The LBP intervention before DEHP exposure experiment (the first experimental method) found that LBP group rats showed a strong capacity toward DEHP detoxification, evidenced by the significant upregulation of activities and concentrations of the partner retinoid, X receptor alpha (RXRα), and downstream regulators Cytochrome P4502E1 (CYP2E1), Cytochrome P4503A1 (CYP3A1), Glutathione S-Transferase Pi (GSTpi), and UDP-glucuronosyltransferase 1 (UGT1) in a dose-dependent manner. The LBP and WJ intervention after DEHP exposure experiment (the second intervention experiment) found that WJ could downregulate pregnane X receptor (PXR), and upregulate downstream regulators, CYP2E1, CYP3A1, and Glutathione S-Transferase (GST) with the extension of intervention time, to alleviate the toxicity of DEHP. However, the intervention effect of WJ was more obvious than that of LBP. These results suggested that LBP and WJ might be effective detoxification agents against DEHP-induced toxic effects, by activating PXR and PXR-related detoxifying enzymes.

Endocrine Disruptors in Water and Their Effects on the Reproductive System

Anthropogenic contaminants in water can impose risks to reproductive health. Most of these compounds are known to be endocrine disrupting chemicals (EDCs). EDCs can impact the endocrine system and subsequently impair the development and fertility of non-human animals and humans. The source of chemical contamination in water is diverse, originating from byproducts formed during water disinfection processes, release from industry and livestock activity, or therapeutic drugs released into sewage. This review discusses the occurrence of EDCs in water such as disinfection byproducts, fluorinated compounds, bisphenol A, phthalates, pesticides, and estrogens, and it outlines their adverse reproductive effects in non-human animals and humans.

Perturbation of Nuclear Hormone Receptors by Endocrine Disrupting Chemicals: Mechanisms and Pathological Consequences of Exposure

Much of the early work on Nuclear Hormone Receptors (NHRs) focused on their essential roles as mediators of sex steroid hormone signaling in reproductive development and function, and thyroid hormone-dependent formation of the central nervous system. However, as NHRs display tissue-specific distributions and activities, it is not surprising that they are involved and vital in numerous aspects of human development and essential for homeostasis of all organ systems. Much attention has recently been focused on the role of NHRs in energy balance, metabolism, and lipid homeostasis. Dysregulation of NHR function has been implicated in numerous pathologies including cancers, metabolic obesity and syndrome, Type II diabetes mellitus, cardiovascular disease, hyperlipidemia, male and female infertility and other reproductive disorders. This review will discuss the dysregulation of NHR function by environmental endocrine disrupting chemicals (EDCs), and the associated pathological consequences of exposure in numerous tissues and organ systems, as revealed by experimental, clinical, and epidemiological studies.

Nonmonotonic Effects of Chronic Low-Dose Di(2-ethylhexyl) Phthalate on Gonadal Weight and Reproductive

Endocrine disruptors have been concerned in toxicology but now challenged as physiological point especially concerned with exposing dose and period. In this study the low-dose chronic administration of di(2-ethylhexyl) phthaltae (DEHP) during reproductive period was examined to evaluate the possible roles. Adult male and female CD-1 mice were exposed to DEHP with drinking water containing 133 1g/L and 1,330 /g/L DEHP in water according to OECD 433 guide line and sacrificed just after weaning. The weights of uterus and ovary were decreased by drinking of 1,330 /g/L DEHP water. There was not adverse effects on either accumulated mating rate and mating rate depend on estrus stage, pregnancy duration, and sex ration at birth. However, the accumulated rate of successful delivery and litter size were significantly high at 1,330 dg/L DEHP water. The number of epididymal sperm was significantly increased by drinking of 1,330 g/L DEHP water. In addition, the number of follicles (primary, secondary, tertiary) were more many than control at 1,330 /g/L DEHP water drunk mother. Though further studies are needed to identify what are the mechanism of DEHP in folliculogenesis and spermatogenesis. From this study we firstly report the effect of low-dose chronic administration of DEHP with drinking could change the ovarian follicle population size and spermatogenesis rate. Put together, those finding is different from previous high-dose effects and suggest the physiological role of DEHP in gonads and uterus.

Maternal phthalate exposure during early pregnancy and at delivery in relation to gestational age and size at birth: A preliminary analysis

Epidemiologic studies of in utero phthalate exposure and birth outcomes have had conflicting findings. The objective of this study was to characterize maternal phthalate exposure across pregnancy, examine associations between maternal phthalate levels and infant size and gestational age at birth, and investigate relationships between concurrent bisphenol A (BPA) and phthalate exposure and birth outcomes. Women in the Michigan Mother-Infant Pairs cohort provided urine and blood samples during their first trimester and at delivery. Urinary phthalate metabolites and serum BPA were measured at both time points, and birth weight, length, head circumference, and gestational age were recorded from medical records. Maternal DEHP metabolite concentrations were significantly higher at delivery compared to the first trimester (p<0.05), suggesting increased DEHP exposure late in pregnancy. A number of phthalate metabolites were associated with birth size and gestational age in patterns that varied by sex and timing of exposure, independent of BPA exposure.

Maternal exposure to di-(2-ethylhexyl) phthalate disrupts placental growth and development in pregnant mice

Di-(2-ethylhexyl) phthalate (DEHP) is used as a plasticizer and widely dispersed in the environment. DEHP exposure reduces embryo implantations, increases embryonic loss, and decreases fetal body weights. However, no detailed information is available about the effect of DEHP on the placentation during pregnancy. Thus, our aim was to explore the effect of DEHP on the growth and development of placenta in vivo. Mice were administered DEHP by gavages at 125, 250, 500 mg/kg/day from gestational days (GD) 1 until sacrifice. Results showed that DEHP treatment significantly reduced the weight of placenta at GD 13. Histopathologically, in DEHP-treated group, the ectoplacental cones significantly became smaller at GD9, and total area of placenta and area of spongiotrophoblast were significantly reduced at GD 13. Expression levels of Ascl2, Esx1 and Fosl1 mRNA dramatically decreased in DEHP-treated placenta at GD 13. DEHP administration disrupted labyrinth vascularization of placentas, and inhibited proliferation and induced apoptosis of placenta by the activation of caspase-3 and -8, up-regulation of Bax and down-regulation of Bcl-2 mRNA and protein at GD 13. In conclusion, these results suggest that adverse pregnancy outcomes including low birth-weight and pregnancy loss exposed to DEHP are possibly mediated, at least in part, via the suppression of placental growth and development.

Di(2-ethylhexyl) phthalate inhibits antral follicle growth, induces atresia, and inhibits steroid hormone production in cultured mouse antral follicles

Di(2-ethylhexyl) phthalate (DEHP) is a ubiquitous environmental toxicant found in consumer products that causes ovarian toxicity. Antral follicles are the functional ovarian units and must undergo growth, survival from atresia, and proper regulation of steroidogenesis to ovulate and produce hormones. Previous studies have determined that DEHP inhibits antral follicle growth and decreases estradiol levels in vitro; however, the mechanism by which DEHP elicits these effects is unknown. The present study tested the hypothesis that DEHP directly alters regulators of the cell cycle, apoptosis, and steroidogenesis to inhibit antral follicle functionality. Antral follicles from adult CD-1 mice were cultured with vehicle control or DEHP (1-100 μg/ml) for 24-96 h to establish the temporal effects of DEHP on the follicle. Following 24-96 h of culture, antral follicles were subjected to gene expression analysis, and media were subjected to measurements of hormone levels. DEHP increased the mRNA levels of cyclin D2, cyclin dependent kinase 4, cyclin E1, cyclin A2, and cyclin B1 and decreased the levels of cyclin-dependent kinase inhibitor 1A prior to growth inhibition. Additionally, DEHP increased the mRNA levels of BCL2-associated agonist of cell death, BCL2-associated X protein, BCL2-related ovarian killer protein, B-cell leukemia/lymphoma 2, and Bcl2-like 10, leading to an increase in atresia. Further, DEHP decreased the levels of progesterone, androstenedione, and testosterone prior to the decrease in estradiol levels, with decreased mRNA levels of side-chain cleavage, 17α-hydroxylase-17,20-desmolase, 17β-hydroxysteroid dehydrogenase, and aromatase. Collectively, DEHP directly alters antral follicle functionality by inhibiting growth, inducing atresia, and inhibiting steroidogenesis.

Exposure to di(2-ethylhexyl) phthalate inhibits luteal function via dysregulation of CD31 and prostaglandin F2alpha in pregnant mice

BACKGROUND

Di(2-ethylhexyl) phthalate (DEHP) exposure reduces embryo implantations, increases embryonic loss, and decreases fetal body weights. However, whether it is associated with the alteration of luteal function remains unknown. Thus, our aim in this study was to explore the effect and mechanism of DEHP on luteal function in pregnant mice in vivo.

METHODS

Mice were administered DEHP by gavage at 125, 250, 500 mg/kg/day from gestational days (GD) 1 to 9 or 13. Levels of serum progesterone and estradiol were measured by radioimmunoassay. The numbers and sizes of corpora lutea were calculated by ovarian histomorphology. Steroidogenic enzymes were assessed by qRT-PCR. CD31 protein was detected by immunocytochemistry, and prostaglandin F2alpha (PGF2alpha) levels were evaluated by enzyme immunoassay.

RESULTS

Treatment with DEHP significantly inhibited progesterone secretion in pregnant mice in a dose-dependent manner but did not inhibit estradiol production on GD 9 and 13. Treatment also showed concomitant decreases in transcript levels for key steroidogenic enzymes (CYP11A, 3β-HSD, and StAR) on GD 13. Furthermore, DEHP administration significantly reduced the numbers and sizes of corpora lutea on GD 13. No significant changes in the ratio of ovary weight vs. body weight were observed between the control group and treated animals on GD 9 and 13. In addition, treatment with DEHP significantly inhibited CD31 expression of corpora lutea, whereas plasma PGF2alpha levels in DEHP treatment groups were significantly higher compared with the control groups on GD 9 and 13.

CONCLUSIONS

The results show DEHP significantly inhibits luteal function of pregnant mice in vivo, with a mechanism that seems to involve the down-regulation of progesterone and steroidogenic enzymes message RNA, the decrease in CD31 expression, and the increase in PGF2alpha secretion.

The effects of phthalates on the ovary

Phthalates are commonly used as plasticizers in the manufacturing of flexible polyvinyl chloride products. Large production volumes of phthalates and their widespread use in common consumer, medical, building, and personal care products lead to ubiquitous human exposure via oral ingestion, inhalation, and dermal contact. Recently, several phthalates have been classified as reproductive toxicants and endocrine-disrupting chemicals based on their ability to interfere with normal reproductive function and hormone signaling. Therefore, exposure to phthalates represents a public health concern. Currently, the effects of phthalates on male reproduction are better understood than the effects on female reproduction. This is of concern because women are often exposed to higher levels of phthalates than men through their extensive use of personal care and cosmetic products. In the female, a primary regulator of reproductive and endocrine function is the ovary. Specifically, the ovary is responsible for folliculogenesis, the proper maturation of gametes for fertilization, and steroidogenesis, and the synthesis of necessary sex steroid hormones. Any defect in the regulation of these processes can cause complications for reproductive and non-reproductive health. For instance, phthalate-induced defects in folliculogenesis and steroidogenesis can cause infertility, premature ovarian failure, and non-reproductive disorders. Presently, there is a paucity of knowledge on the effects of phthalates on normal ovarian function; however, recent work has established the ovary as a target of phthalate toxicity. This review summarizes what is currently known about the effects of phthalates on the ovary and the mechanisms by which phthalates exert ovarian toxicity, with a particular focus on the effects on folliculogenesis and steroidogenesis. Further, this review outlines future directions, including the necessity of examining the effects of phthalates at doses that mimic human exposure.

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.

Impact of environmental exposures on ovarian function and role of xenobiotic metabolism during ovotoxicity

The mammalian ovary is a heterogeneous organ and contains oocyte-containing follicles at varying stages of development. The most immature follicular stage, the primordial follicle, comprises the ovarian reserve and is a finite number, defined at the time of birth. Depletion of all follicles within the ovary leads to reproductive senescence, known as menopause. A number of chemical classes can destroy follicles, thus hastening entry into the menopausal state. The ovarian response to chemical exposure can determine the extent of ovotoxicity that occurs. Enzymes capable of bioactivating as well as detoxifying xenobiotics are expressed in the ovary and their impact on ovotoxicity has been partially characterized for trichloroethylene, 7,12-dimethylbenz[a]anthracene, and 4-vinylcyclohexene. This review will discuss those studies, as well as illustrate where knowledge gaps remain for chemicals that have also been established as ovotoxicants.

Peroxisome proliferator-activated receptors as mediators of phthalate-induced effects in the male and female reproductive tract: epidemiological and experimental evidence

There is growing evidence that male as well as female reproductive function has been declining in human and wildlife populations over the last 40 years. Several factors such as lifestyle or environmental xenobiotics other than genetic factors may play a role in determining adverse effects on reproductive health. Among the environmental xenobiotics phthalates, a family of man-made pollutants are suspected to interfere with the function of the endocrine system and therefore to be endocrine disruptors. The definition of endocrine disruption is today extended to broader endocrine regulations, and includes activation of metabolic sensors, such as the peroxisome proliferator-activated receptors (PPARs). Toxicological studies have shown that phthalates can activate a subset of PPARs. Here, we analyze the epidemiological and experimental evidence linking phthalate exposure to both PPAR activation and adverse effects on male and female reproductive health.

Novel organization of the genes for phthalate degradation from Burkholderia cepacia DBO1

Burkholderia cepacia DBO1 is able to utilize phthalate as the sole source of carbon and energy for growth. Two overlapping cosmid clones containing the genes for phthalate degradation were isolated from this strain. Subcloning and activity analysis localized the genes for phthalate degradation to two separate regions on the cosmid clones. Analysis of the nucleotide sequence of these two regions showed that the genes for phthalate degradation are arranged in at least three transcriptional units. The gene for phthalate dioxygenase reductase (ophA1) is present by itself, while the genes for an inactive transporter (ophD) and 4,5-dihydroxyphthalate decarboxylase (ophC) are linked and the genes for phthalate dioxygenase oxygenase (ophA2) and cis-phthalate dihydrodiol dehydrogenase (ophB) are linked. ophA1 and ophDC are adjacent to each other but are transcribed in opposite directions, while ophA2B is located 4 kb away. The genes for the oxygenase and reductase components of phthalate dioxygenase are located approximately 7 kb away from each other. The gene for the putative phthalate permease contains a frameshift mutation in contrast to genes for other permeases. Strains deleted for ophD are able to transport phthalate into the cell at rates equivalent to that of the wild-type organism, showing that this gene is not required for growth on phthalate.

An in vivo and in vitro study of the loss of plasticizer from soft polymer-gel materials

Polymer-gel materials used as short-term denture soft linings are blended with plasticizers to lower the glass transition temperature (Tg). A lower Tg allows for greater polymer chain mobility, thus producing a more flexible material. The present work evaluated the loss of plasticizers due to leaching both in vivo and in vitro. Two commercial denture soft-lining materials (A and B) were tested. These were both poly(ethyl methacrylate) polymers, blended with alcohol and phthalate esters. A clinical study was conducted in which patients wore, sequentially, dentures bearing (on separate occasions) each of the two soft-polymer lining materials. The two materials A and B were randomly assigned for each of ten patients and were worn for 14 and 30 days, respectively. With one exception, patients wore dentures with both lining materials, for a total of 19 clinical evaluations. The plasticizer loss occurring during the clinical trial was determined by GC analysis from the initial and terminal day sampling of plasticizer content of the soft polymer-gel materials. The results of this analysis were compared with results obtained from an in vitro leachability study by use of sink conditions in water at 37 degrees C for the same two commercial soft polymers conducted over the same time periods of 14 and 30 days. The results indicated that a higher loss of plasticizer occurred in vivo, compared with the in vitro tests for 17 of the 19 clinical evaluations. The average plasticizer lost in vivo from material A at 14 days was 122 +/- 58 mg/g, and for material B at 30 days it was 33 +/- 27 mg/g.(ABSTRACT TRUNCATED AT 250 WORDS)

Mono-2-ethylhexyl phthalate, a metabolite of di-(2-ethylhexyl) phthalate, causally linked to testicular atrophy in rats

Acute testicular atrophy results when appropriate dosages of di-(2-ethylhexyl) phthalate (DEHP) or its hydrolysis product mono-2-ethylhexyl phthalate (MEHP) are given to male rats. Events thought to be involved in this pathological effect also occur in cultures of testicular cells in vitro, but require MEHP rather than DEHP. Primary cultures of hepatocytes, Sertoli cells, and Leydig cells were incubated with 14C-labeled MEHP [8 microM] for up to 24 hr. No significant reduction in viability was produced under these conditions. In contrast to the hepatocytes, which extensively metabolized MEHP to a variety of products in 1 hr, the testicular cell cultures were apparently unable to metabolize MEHP (beyond a slight hydrolysis to phthalic acid by Sertoli cells) in 18-24 hr. MEHP was efficiently taken up by hepatocytes, but much less so by testicular cells. These results, combined with related observations from the literature, support the hypothesis that MEHP itself is the metabolite of DEHP responsible for testicular atrophy in rats.

Di-(2-ethylhexyl)-phthalate as plasticizer in PVC respiratory tubing systems: indications of hazardous effects on pulmonary function in mechanically ventilated, preterm infants

Several PVC medical devices contain the plasticizer Di-(2-ethylhexyl)-phthalate (DEHP) in high concentration. Taken systematically DEHP only has minor toxic effects in the human organism. In three preterm infants artificially ventilated with PVC respiratory tubes unusual lung disorders resembling those observed in hyaline membrane disease, verified both clinically and radiologically, were observed during the fourth week of life. It was assumed that these lung disorders were causally related to the exposure to high doses of DEHP, which was released from the walls of the respiratory tubes. DEHP was found in the lung tissue of one patient who died of pneumothorax soon after birth after being artificially ventilated. It is strongly recommended that for disposable PVC respiratory devices the plasticizer DEHP should be used with more restrictions.