Subchronic Exposure to Di(2-ethylhexyl) Phthalate and Diisononyl Phthalate During Adulthood Has Immediate and Long-Term Reproductive Consequences in Female Mice

Maternal preconception phthalate metabolite concentrations in follicular fluid and neonatal birth weight conceived by women undergoing in vitro fertilization

Exposure to phthalates during gestation has been associated with decreased birth weight among offspring. However, the associations between preconception phthalate metabolites in follicular fluid (FF) and offspring birth weight among women undergoing in vitro fertilization (IVF) remain largely unknown. Here, we explored the associations between preconception phthalate metabolite concentrations in FF and the birth weights of singletons and twins among women undergoing IVF. We recruited 147 female participants who gave birth to 90 singletons and 57 twin infants at the Reproductive Medicine Center, Tongji Hospital, Wuhan, between November and December 2016. Each participant was asked to complete a questionnaire at the time of recruitment and provide a FF sample on the day of oocyte retrieval. The FF concentrations of eight phthalate metabolites were determined using high-performance liquid chromatography and tandem mass spectrometry. Birth outcomes were abstracted from medical records. The associations between phthalate metabolites in FF and birth weights of the singleton and twin groups were evaluated using generalized linear models (GLMs). We found that birth weight in the twin group had negative dose-response associations with maternal preconception monobenzyl phthalate (MBzP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) in FF (both P for trends < 0.05) and that birth weight in the singleton group had positive dose-response associations with monoethyl phthalate (MEP) and mono(2-ethyl-5 hydroxyhexyl) phthalate (MEHHP) in FF (both P for trends < 0.05). These associations persisted when we modeled as continuous variables. In addition, we observed male-specific association between decreased twin birth weight and MEOHP and MBzP and a female-specific associations between increased singleton birth weight and MEP, MEHHP and the sum of di(2-ethylhexyl) phthalate (∑DEHP) (all P for interactions < 0.05). Preconception phthalate metabolites in maternal FF may affect the birth weights of both singleton and twin newborns.

Prenatal exposure to an environmentally relevant phthalate mixture accelerates biomarkers of reproductive aging in a multiple and transgenerational manner in female mice

Phthalates are known endocrine-disrupting chemicals that are found in many consumer products. Our laboratory previously developed a relevant phthalate mixture consisting of six phthalates and found that it disrupted female fertility in mice. However, it is unknown if prenatal exposure to phthalate mixtures can accelerate reproductive aging and if this occurs in multiple generations. Thus, we tested the hypothesis that prenatal exposure to a mixture of phthalates accelerates biomarkers of reproductive aging in multiple generations of female mice. Pregnant CD-1 mice were orally dosed with vehicle control or a phthalate mixture (20 μg/kg/day-500 mg/kg/day) daily from gestational day 10 to birth. Adult F1 females born to these dams were used to create the F2 and F3 generations by mating them with unexposed males. At 13 months, estrous cyclicity was monitored and ovaries and sera were collected for analysis. In the F1 generation, the mixture decreased testosterone and inhibin B levels, but increased follicle-stimulating hormone and luteinizing hormone levels compared to control. In the F2 generation, the phthalate mixture decreased the percent of antral follicles and testosterone hormone levels compared to control. In the F3 generation, prenatal exposure to the phthalate mixture increased ovarian weight, increased the time in metestrus/diestrus, altered follicle numbers, and decreased the levels of luteinizing hormone compared to control. Collectively, these data suggest that prenatal exposure to a phthalate mixture may accelerate several biomarkers of reproductive aging in a multi- and transgenerational manner in female mice.

The effects of the phthalate DiNP on reproduction†

Di-isononyl phthalate (DiNP) is a high molecular weight, general purpose, plasticizer used primarily in the manufacture of polymers and consumer products. It can be metabolized rapidly and does not bioaccumulate. The primary metabolite of DiNP is monoisononyl-phthalate (MiNP) and the secondary metabolites include three oxidative derivatives of DiNP, which have been identified mainly in urine: mono-oxoisononyl phthalate (MOINP or oxo-MiNP), mono-carboxyisooctyl phthalate (MCIOP, MCOP or cx-MiNP), and mono-hydroxyisononyl phthalate (MHINP or OH-MiNP). The secondary metabolites are very sensitive biomarkers of DiNP exposure while primary metabolites are not. As the usage of DiNP worldwide increases, studies evaluating its potential reproductive toxicity are becoming more prevalent in the literature. In studies on female animals, the researchers found that the exposure to DiNP appears to induce negative effects on ovarian function and fertility in animal models. Whether or not DiNP has direct effects on the uterus is still controversial, and the effects on human reproduction require much more research. Studies on males indicate that DiNP exposure has disruptive effects on male reproduction and fertility. Occupational studies also indicate that the exposure to DiNP might induce negative effects on male reproduction, but larger cohort studies are needed to confirm this. This review presents an overview of the literature regarding the reproductive effects of exposure to DiNP.

An update on the hazard of and exposure to diethyl hexyl phthalate (DEHP) alternatives used in medical devices

The use of the plasticizer diethyl hexyl phthalate (DEHP) in PVC medical devices is being questioned due to its potential reprotoxic effects in patients exposed as a result from migration from the device. This article reviews new information on migration and toxicity data of eleven alternative plasticizers that have previously been evaluated by the Danish EPA and the EU SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks). The new toxicity data did not justify the reconsideration of the critical NOAELs as established by SCENIHR and Danish EPA. The dataset on oral toxicity studies is rather complete for most substances; however, in particular for reproductive toxicity and endocrine disruption, data gaps still exist for many alternatives. Toxicity data on intravenous exposure are lacking and these are essential to conclude on hazard characteristics of alternatives that are poorly absorbed via the oral exposure route. Migration data are emerging for a few alternatives but still sparse for the majority of the alternatives. Taking all data on migration and toxicity in consideration, 1,2-cyclohexanedicarboxylic acid, diisononylester (DINCH), and tris(2-ethylhexyl)benzene-1,2,4-tricarboxylate display a more favorable profile compared to DEHP. For these promising alternatives, a risk assessment for use in medical devices should be conducted. As a next step, we recommend the (further) generation of relevant migration data and, where needed, relevant toxicity data for the alternative substances, in order to be able to conduct a benefit-risk analysis of DEHP and the alternatives as obligatory in the new European Union Medical Device Regulation.

The Impact of Environmental Chemicals on the Gut Microbiome

Since the surge of microbiome research in the last decade, many studies have provided insight into the causes and consequences of changes in the gut microbiota. Among the multiple factors involved in regulating the microbiome, exogenous factors such as diet and environmental chemicals have been shown to alter the gut microbiome significantly. Although diet substantially contributes to changes in the gut microbiome, environmental chemicals are major contaminants in our food and are often overlooked. Herein, we summarize the current knowledge on major classes of environmental chemicals (bisphenols, phthalates, persistent organic pollutants, heavy metals, and pesticides) and their impact on the gut microbiome, which includes alterations in microbial composition, gene expression, function, and health effects in the host. We then discuss health-related implications of gut microbial changes, which include changes in metabolism, immunity, and neurological function.

Exposure to di(2-ethylhexyl) phthalate and diisononyl phthalate during adulthood disrupts hormones and ovarian folliculogenesis throughout the prime reproductive life of the mouse

Di(2-ethylhexyl) phthalate (DEHP) is a phthalate commonly used for its plasticizing capabilities. Because of the wide production and use of DEHP, humans are exposed to DEHP on a daily basis. Diisononyl phthalate (DiNP) is often used as a DEHP replacement chemical, and because of the increased use of DiNP, humans are increasingly exposed to DiNP over time. Of concern is that DEHP and DiNP both exhibit endocrine disrupting capabilities, and little is known about how short-term exposure to either of these phthalates affects aspects of female reproduction. Thus, this study tested the hypothesis that short-term exposure to DEHP or DiNP during adulthood has long-lasting consequences on ovarian follicles and hormones in female mice. Female CD-1 mice aged 39-40 days were orally dosed with either vehicle control (corn oil), DEHP (20 μg/kg/day-200 mg/kg/day), or DiNP (20 μg/kg/day-200 mg/kg/day) for 10 days. Ovarian follicle populations, estradiol, testosterone, progesterone, follicle stimulating hormone (FSH), and inhibin B were analyzed at time points immediately post-dosing and 3, 6, and 9 months post-dosing. The results indicate that 10 days of exposure to DEHP and DiNP changed the distribution of ovarian follicle populations and sex steroid hormones at multiple time points, including the last time point, 9 months post-dosing. Further, FSH was increased at multiple doses up to 6 months post-dosing. Inhibin B was not affected by treatment. These data show that short-term exposure to either DEHP or DiNP has long-term consequences that persist long after cessation of exposure.

Lifestyle and environmental contributions to ovulatory dysfunction in women of polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common reason of anovulatory infertility. Environmental factor is one of the main causes of PCOS, but its contribution to ovulatory dysfunction in PCOS remains unknown.

METHODS

A total of 2217 infertile women diagnosed as PCOS according to Rotterdam criteria were recruited, including 1979 women with oligo-anovulation (OA group) and 238 women with normal -anovulation (non OA group). Besides, 279 healthy control women of reproductive age were enrolled as controls.

RESULTS

Frequencies of snoring (PCOS-OA group, PCOS-non-OA group, control group: 29.30% vs 18.10% vs 11.50%, P < 0.01), smoking (37.70% vs 28.10% vs 12.20%, P < 0.01), plastic tableware usage (38.30% vs 28.10% vs 25.40%, P < 0.01) and indoor decoration (32.10% vs 24.80% vs 16.80%, P < 0.01) were highest in PCOS-OA group. After adjusted for multivariable, difference remained significant between PCOS-OA group and the other two groups. PCOS-OA women preferred a meat favorable diet compared to PCOS-non-OA group (54.60% vs 41.30%, P < 0.01). There was no difference between three groups in exercise, frequency of insomnia, and alcohol consumption.

CONCLUSIONS

Smoking, snoring, hyper-caloric diet, plastic tableware usage and indoor decoration were found to be associated with an increased risk for ovulatory dysfunction in women suffering from PCOS.

Late-life consequences of short-term exposure to di(2-ethylhexyl) phthalate and diisononyl phthalate during adulthood in female mice

Di(2-ethylhexyl) phthalate (DEHP) is a known endocrine disruptor and diisononyl phthalate (DiNP) is a common DEHP replacement chemical. However, little is known about late-life consequences due to DEHP or DiNP exposure during adulthood. Thus, this study tested the hypothesis that adult exposure to DEHP or DiNP affects female reproductive parameters during late-life in female mice. Female CD-1 mice (age 39-40 days) were dosed with either vehicle control, DEHP (20 μg/kg/day-200 mg/kg/day), or DiNP (20 μg/kg/day-200 mg/kg/day) for 10 days and breeding trials were conducted at 12 and 15 months post-dosing. Further, ovaries and sera were collected at 12, 15, and 18 months post-dosing. DEHP and DiNP disrupted estrous cyclicity, increased pregnancy loss, decreased fertility, altered the sex ratio of pups, altered ovarian follicle populations, and disrupted hormone levels. Collectively, these data show that short-term exposure to DEHP or DiNP during adulthood has long-term consequences in late-life.

Alterations in oocytes and early zygotes following oral exposure to di(2-ethylhexyl) phthalate in young adult female mice

Because di(2-ethylhexyl) phthalate (DEHP) toxicity on ovarian function is incomplete, effects of DEHP oocyte fertilization and the resulting zygotes were investigated. Further, an analysis characterizing the stage of zygote arrest was performed. Female CD1 mice were dosed orally with DEHP (0, 20, 200 and 2000 μg/kg/day) for 30 days. Following an in vivo mating post-dosing, DEHP-treated females exhibited fewer oocytes/zygotes, fewer oocytes displaying the polar body extrusion, fewer 1-cell zygotes having 2-pronuclei, more unfertilized oocytes, and decreased number of zygotes at every stage of development. DEHP induced blastomere fragmentation in zygotes. DNA replication in zygotes directly assessed by the 5-Ethynyl-2'-deoxyuridine (5-EdU) incorporation assay and indirectly by dosing mice with 5-fluorouracil (5-FU) suggested that DEHP inhibits DNA replication. Our data suggest that DEHP at doses found in 'every-day' (200 μg/Kg/day) or occupational (2000 μg/Kg/day) environments induces zygote fragmentation and arrests its development from the 2-cell stage potentially impairing DNA replication.

Biodegradation of Structurally Diverse Phthalate Esters by a Newly Identified Esterase with Catalytic Activity toward Di(2-ethylhexyl) Phthalate

Herein, we report a double enzyme system to degrade 12 phthalate esters (PAEs), particularly bulky PAEs, such as the widely used bis(2-ethylhexyl) phthalate (DEHP), in a one-pot cascade process. A PAE-degrading bacterium, Gordonia sp. strain 5F, was isolated from soil polluted with plastic waste. From this strain, a novel esterase (GoEst15) and a mono(2-ethylhexyl) phthalate hydrolase (GoEstM1) were identified by homology-based cloning. GoEst15 showed broad substrate specificity, hydrolyzing DEHP and 10 other PAEs to monoalkyl phthalates, which were further degraded by GoEstM1 to phthalic acid. GoEst15 and GoEstM1 were heterologously coexpressed in Escherichia coli BL21 (DE3), which could then completely degrade 12 PAEs (5 mM), within 1 and 24 h for small and bulky substrates, respectively. To our knowledge, GoEst15 is the first DEHP hydrolase with a known protein sequence, which will enable protein engineering to enhance its catalytic performance in the future.