Mary J. Laws

Phthalates are plasticizers and solvents used in numerous consumer products. Exposure to a phthalate mixture (Mix) alters estrous cyclicity, fertility indices, ovarian follicle dynamics, and steroidogenesis. In cultured antral follicles, phthalates alter the aryl hydrocarbon receptor (AHR) pathway, which is known for estradiol (E2) and xenobiotic metabolism. However, how phthalates affect the AHR pathway in the ovary in vivo and how this pathway changes throughout the reproductive lifespan are unknown. Thus, we hypothesized that expression and localization of genes and proteins in the AHR pathway change throughout the reproductive lifespan and in response to Mix exposure. We exposed adult female CD-1 mice to corn oil control or varying doses (0.15, 1.5, or 1,500 ppm) of Mix for 1 to 12 months. Sera and ovaries were collected at each time point. Sera were used to determine circulating E2 concentrations. The AHR pathway in the ovaries was examined using quantitative polymerase chain reaction for gene expression, RNAscope in situ hybridization for transcript localization, and immunohistochemistry for protein localization. The AHR pathway was altered throughout the reproductive lifespan, with increased Cyp1a1 expression and decreased CYP1B1 protein localization in the ovary at 13 months of age. Circulating E2 decreased throughout aging. Mix exposure altered Arnt and Ahr expression after 1 and 12 months, respectively. Additionally, Mix exposure increased CYP1A1 protein localization after 6 months, with areas of increased staining intensity in the ovary. Overall, the AHR pathway was altered with reproductive aging, and Mix exposure affected the pathway over time.

Di(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DiNP) are plasticizers used in many consumer products. Both phthalates alter estrous cyclicity, fertility indices, and folliculogenesis throughout the reproductive lifespan. Our companion paper showed that exposure to a phthalate mixture containing DEHP and DiNP altered the aryl hydrocarbon receptor (AHR) signaling pathway in the ovary. However, limited information was available on how DEHP and DiNP individually affect the AHR signaling pathway in the ovary throughout reproductive aging. Thus, we hypothesized that DEHP and DiNP individually affect the gene and protein expression and localization associated with the AHR pathway throughout the reproductive lifespan. We treated adult female CD-1 mice with corn oil control or doses (0.15 ppm, 1.5 ppm, or 1,500 ppm) of DEHP and DiNP in the diet for 1 to 12 mo. Sera were used to measure circulating estradiol (E2) concentrations. The AHR pathway was assessed using quantitative PCR (qPCR) for gene expression, RNAscope in situ hybridization for transcript localization, and immunohistochemistry for protein localization. Exposure to DEHP, but not DiNP, reduced serum E2 after 1 mo compared with control. DEHP exposure increased Cyp1a1 expression and CYP1B1 localization in the ovary after 6 mo compared with control. DiNP also increased Arnt expression and CYP1B1 localization in the ovary after 1 mo compared with control. DiNP exposure decreased Ahr and Cyp1a1 expression as well as CYP1A1 localization in the antral follicle after 12 mo compared with control. Overall, DEHP and DiNP both influence the ovarian AHR pathway, but at different time points and doses.

Adipose tissue plays a critical role in metabolic and endocrine function because it is essential for maintaining systemic energy homeostasis and other related physiological functions. Mammals have 4 types of adipose tissue: white adipose tissue (WAT), brown adipose tissue (BAT), beige or brite adipose tissue (BeAT), and pink adipose tissue (PAT). These adipose tissues release endocrine factors that modulate diverse processes such as energy storage and expenditure, appetite control, glucose homeostasis, insulin sensitivity, inflammation, lipid metabolism, tissue repair, thermogenesis, and milk production. Proper adipose tissue function relies on hormone receptors and signaling pathways that make the adipose tissues susceptible to disruption by endocrine-disrupting chemicals such as phthalates. Here, we review relevant research on the associations between phthalate exposures and abnormalities in WAT and BAT functions, including phthalate-induced changes in morphology, physiology, and gene expression. This review covers in vitro studies, in vivo studies in mammals, and studies in humans. We also discuss important gaps in the literature. Overall, the evidence indicates that phthalates adversely affect WAT and BAT functions. Further studies are needed to better elucidate the mechanisms through which phthalates act in the adipose tissues and to determine the effects of phthalates on human adipose tissues.

Polystyrene nanoplastics (PS-NPs) are small particles derived from plastic degradation that have been detected in several human tissues. Phthalates are ubiquitous plasticizers used to increase flexibility in polymers which act as endocrine disruptors, impacting hormonal homeostasis. Considering that both pollutants have been detected in human follicular fluid, there is increasing concern regarding their potential effects on female reproductive health. This study evaluated the isolated and combined effects of environmentally relevant doses of PS-NPs and a phthalate metabolite mixture (MM) on antral follicle growth, hormone production, and the expression of genes involved in apoptosis, oxidative stress, steroidogenesis, and hormone receptor signaling. Antral follicles from adult CD-1 mice were cultured with vehicle control (DMSO and water), metabolite mixture (0.01, 0.1, 1, and 10 μg/ml), or PSNPs (5, 25, 50, and 100 μg/ml) or MM + PS-NPs (5 µg/ml PS-NPs + 0.01 µg/ml MM; 100 μg/ml PS-NPs + 10 μg/ml MM). Follicle growth was monitored every 24 h for 96 h. PS-NPs and MM were internalized by follicles and they inhibited follicle growth alone and in co-exposure. Both pollutants altered the expression of apoptosis-related (Casp3, Casp8, Bcl2) and oxidative stress-related (Cat, Nrf2, Gpx1) genes without significantly affecting steroid hormone levels. Co-exposure also reduced Esr2 and Ar expression, demonstrating more pronounced effects under low-dose combined exposure. Altogether, these findings indicate that environmentally relevant exposure to PS-NPs and phthalate mixtures impairs antral follicle growth and disrupts molecular pathways essential for ovarian function, highlighting potential pathways and the importance of understanding combined exposures in reproductive toxicity.

Phthalates are ubiquitous endocrine-disrupting chemicals whose exposure is associated with accelerated reproductive aging in humans. We focused on the pituitary gland, the source of the gonadotropins: Follicle-stimulating hormone (FSH) and luteinizing hormone (LH). We hypothesized that the common phthalates di-(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DiNP) modulate inflammation in the pituitary and impact gonadotropin expression acutely and during aging. To test this, female CD-1 mice were orally dosed with corn oil or varying concentrations of DEHP and DiNP for 10 days. Pituitary tissues were collected immediately after dosing or 15 months post-dosing, processed, and analyzed by quantitative real-time PCR (qPCR) and immunohistochemistry. We found that acute phthalate exposure did not alter Fshb and Lhb mRNA expression compared with controls, but both DEHP and DiNP reduced FSH immunopositive cell number. Phthalate exposure also decreased Il1b, and increased Il18 and Tnf mRNA levels compared with controls, suggesting an inflammatory imbalance. At 15 months post-dosing, DiNP exposure increased Lhb and Il1b mRNA levels, but repressed Fshb and Nlrp3 mRNA levels compared with controls. Next, using dissociated cultures, we investigated the impact of phthalates and the proinflammatory stimulus lipopolysaccharide (LPS) on inflammation and gonadotropin gene expression directly at the pituitary. Both the DEHP metabolite MEHP and LPS decreased Fshb, but not Lhb mRNA relative to control. MEHP also repressed the induction of Il1b by LPS. Together, these findings suggest that acute exposure to phthalate alters mRNA expression of inflammatory markers and gonadotropins in the pituitary, which could alter the process of reproductive aging.

Endocrine-disrupting chemicals such as di(2-ethylhexyl) phthalate (DEHP) pose significant risks to human reproductive health. However, regulatory frameworks often lack sufficient data on sensitive female-specific reproductive endpoints. This study investigates the sensitivity of hypothalamic–pituitary–ovarian (HPO) axis endpoints to DEHP exposure in adult female mice, applying Bayesian Benchmark dose (BBMD) modeling for dose–response assessment and derivation of points-of-departure (PODs) for risk assessment. Data from four studies where sexually mature female mice were exposed to DEHP (0.02 to 240 mg/kg bw/d) for 10 or 30 d via oral administration, or 30 d via diet, was modeled. Endpoints included ovarian follicle counts, serum hormones, estrous cyclicity, body, and organ weights. Results revealed dose-dependent changes and greater sensitivity of progesterone, ovarian follicle counts, and uterine weight, compared with estrous cyclicity, body weight, and other organ weights. For 10- and 30-d oral administration studies, the lowest nonzero BBMDLs were observed for serum progesterone levels (9.1 mg/kg bw/d) and primary follicle counts (19.5 mg/kg bw/d), respectively. These PODs were notably lower than most No-Adverse-Effect-Levels in the European Chemicals Agency’s (ECHA’s) “Registered substances factsheet” and “ECHA CHEM” databases. The majority of the studies derived PODs based on male (reproductive) endpoints. Finally, a derived no-effect level of 0.064 mg DEHP/kg bw/d was estimated, based on the overall lowest BBMDL, serum progesterone levels of the 10-d oral study. In conclusion, our study indicates that current guidelines may not fully capture reproductive risks for females, underscoring the need to refine regulatory endpoints to better protect female reproductive health in the context of DEHP exposure.

Phthalate monoesters have been identified as endocrine disruptors in a variety of models, yet understanding of their exact mechanisms of action and molecular targets in cells remains incomplete. Here, we set to determine whether epidemiologically relevant mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) can affect biological processes by altering cell plasma membrane fluidity or formation of cell-cell contacts. As a model system, we chose endometrial stromal cell lines, one of which was previously used in a transcriptomic study with MEHHP or MEHHP-containing mixtures. A short-term exposure (1 h) of membrane preparations to endocrine disruptors was sufficient to induce changes in membrane fluidity/rigidity, whereas different mixtures showed different effects at various depths of the bilayer. A longer exposure (96 h) affected the ability of cells to form spheroids and highlighted issues with membrane integrity in loosely assembled spheroids. Finally, in spheroids assembled from T-HESC cells, MEHHP interfered with the formation of tight junctions as indicated by the immunostaining of zonula occludens 1 protein. Overall, this study emphasized the need to consider plasma membrane, membrane-bound organelles, and secretory vesicles as possible biological targets of endocrine disruptors and offered an explanation for a multitude of endocrine disruptor roles documented earlier.

Purpose To investigate follicular fluid (FF) phthalate levels in adolescents undergoing fertility preservation compared to oocyte donors and explore its association with ovarian reserve and cumulus cell gene expression. Methods 20 Adolescents (16.7 ± 0.6 years old) and 24 oocyte donors (26.2 ± 0.4 years old) undergoing fertility preservation were included in the study. Patient demographics, ovarian stimulation and oocyte retrieval outcomes were analyzed for each group. FF levels of 9 phthalate metabolites were assessed individually and as molar sums representative of common compounds (all phthalates: ƩPhthalates; DEHP: ƩDEHP), exposure sources (plastics: ƩPlastic; personal care products: ƩPCP), and modes of action (anti-androgenic: ƩAA) and compared between the two groups. Results Follicular fluid ƩPlastic and ƩPCP levels were significantly higher in adolescents compared to oocyte donors (pConclusion Adolescents undergoing fertility preservation cycles demonstrate higher levels of phthalate metabolites in their follicular fluid compared to oocyte donors. Phthalate metabolite levels in FF are associated with higher AFC levels in oocyte donors. Higher phthalate levels in FF are associated with alterations in the cumulus cells transcriptome in adolescents. Capsule Summary Phthalates are detected in the follicular fluid of adolescents and oocytes donors, and the levels are increased in the follicular fluid of adolescents. Higher total phthalate levels in follicular fluid are associated with altered cumulus cells transcriptome in adolescents.

Imidacloprid is a neonicotinoid pesticide used in large-scale agricultural systems, home gardens, and veterinary pharmaceuticals. Imidacloprid is a small molecule that is more water-soluble than other insecticides, increasing the likelihood of large-scale environmental accumulation and chronic exposure of non-targeted species. Imidacloprid can be converted to the bioactive metabolite desnitro-imidacloprid in the environment and body. Little is known about the mechanisms by which imidacloprid and desnitro-imidacloprid induce ovarian toxicity. Thus, we tested the hypothesis that imidacloprid and desnitro-imidacloprid differentially affect antral follicle growth and steroidogenesis in vitro. Antral follicles were dissected from the ovaries of CD-1 mice and cultured in media containing vehicle control or 0.2 µg/mL–200 µg/mL of imidacloprid or desnitro-imidacloprid for 96 h. Follicle morphology was monitored, and follicle size was measured every 24 h. At the end of the culture periods, media were used to quantify follicular hormone levels, and follicles were used for gene expression analysis of steroidogenic regulators, hormone receptors, and apoptotic factors. Imidacloprid did not affect follicle growth or morphology compared to the control. Desnitro-imidacloprid inhibited follicle growth and caused follicles to rupture in culture compared to the control. Imidacloprid increased progesterone, whereas desnitro-imidacloprid decreased testosterone and progesterone compared to the control. Desnitro-imidacloprid also changed estradiol compared to the control. At 48 h, IMI decreased the expression of Star, Cyp17a1, Hsd17b1, Cyp19a1, and Esr2 and increased the expression of Cyp11a1, Cyp19a1, Bax, and Bcl2 compared to the control. IMI also changed the expression of Esr1 compared to the control. At 48 h, DNI decreased the expression of Cyp11a1, Cyp17a1, Hsd3b1, Cyp19a1, and Esr1 and increased the expression of Cyp11a1, Hsd3b1, and Bax compared to the control. At 72 h of culture, IMI significantly decreased the expression of Cyp19a1 and increased the expression of Star and Hsd17b1 compared to the control. At 72 h, DNI significantly decreased the expression of Cyp11a1, Cyp17a1, Hsd3b1, and Bax and increased the expression of Esr1 and Esr2. At 96 h, IMI decreased the expression of Hsd3b1, Cyp19a1, Esr1, Bax, and Bcl2 compared to the control. At 96 h, DNI decreased the expression of Cyp17a1, Bax, and Bcl2 and increased the expression of Cyp11a1, Hsd3b1, and Bax compared to the control. Together, these data suggest mouse antral follicles are targets of neonicotinoid toxicity, and the mechanisms of toxicity differ between parent compounds and metabolites.