(91) Exposure to Diisononyl Phthalate Throughout the Reproductive Lifespan Disrupts Proper Ovarian Function

Adira M. Safar, Ramsés Santacruz-Márquez, Mary J. Laws, Jodi A. Flaws

Department of Comparative Biosciences, University of Illinois Urbana-Champaign, USA

Abstract Text:

The ovary is an essential component of the female reproductive system, as it is responsible for fertility and sex steroid hormone synthesis. Endocrine disrupting chemicals such as phthalates target the ovary. Phthalates are found in numerous products including food packaging, medical tubing, children’s toys, and personal care products. Humans are ubiquitously exposed to phthalates, primarily through ingestion. One such phthalate is diisononyl phthalate (DiNP). A previous study from our lab indicates that short- and long-term adulthood exposure to DiNP induces ovarian toxicity by altering circulating follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels and dysregulating ovarian follicle dynamics. Another study from our lab found that exposure to a phthalate mixture containing DiNP induces ovarian toxicity by increasing ovarian apoptosis and dysregulating ovarian estrogen receptor expression, steroidogenesis, and folliculogenesis. Although these studies provide insight into the effects of DiNP on the ovary, the impacts of exposure to DiNP throughout the reproductive lifespan on the ovary have not been examined. Thus, we investigated the effects of DiNP exposure throughout the reproductive lifespan on ovarian steroidogenesis and folliculogenesis. Female CD-1 mice were exposed to DiNP (0.15, 1.5, or 1500 ppm) through the chow for 12 months. Following exposure, ovaries and sera were collected. Ovaries were used in qPCR analyses of steroidogenic enzymes (Cyp11a1, Cyp17a1, Cyp19a1, Hsd3b1, Hsd17b1, and Star), hormone receptors (Ar, Esr1, Esr2, Fshr, and Lhcgr), and apoptosis regulators (Casp3, Bax, and Bcl2). Sera were analyzed for levels of estradiol, testosterone, FSH, and LH. Histological evaluation of ovarian follicle populations was also performed. DiNP exposure (1.5 ppm) borderline decreased ovarian Star expression compared to control. DiNP exposure (0.15 and 1500 ppm) significantly decreased ovarian Cyp19a1 expression compared to control. Exposure to DiNP did not significantly affect ovarian expression of Cyp11a1, Cyp17a1, Hsd3b1, or Hsd17b1. Interestingly, DiNP exposure did not significantly affect serum estradiol concentrations or ovarian Esr2 expression; however, DiNP exposure (1.5 ppm) borderline decreased ovarian Esr1 expression compared to control. Exposure to DiNP did not significantly affect circulating testosterone levels; however, DiNP exposure (1.5 ppm) significantly decreased ovarian Ar expression compared to control. Additionally, DiNP exposure did not significantly affect serum FSH concentrations or ovarian Fshr expression compared to control. Exposure to DiNP did not significantly affect circulating LH levels; however, DiNP exposure (0.15 and 1.5 ppm) borderline increased ovarian Lhcgr expression compared to control. Interestingly, DiNP exposure did not affect the percentage of primordial, primary, preantral, or antral follicles; however, DiNP exposure (1500 ppm) significantly increased the percentage of atretic follicles compared to control. Additionally, DiNP exposure (1.5 ppm) significantly increased ovarian Casp3 expression compared to control, but the exposure did not significantly affect ovarian expression of Bax or Bcl2. These data indicate that DiNP exposure throughout the reproductive lifespan dysregulates ovarian steroidogenesis without altering sex steroid or gonadotropin hormone levels, dysregulates ovarian receptivity to estrogen, androgens, and LH, and increases ovarian apoptosis and follicular atresia. Together, these data support the hypothesis that exposure to DiNP throughout the reproductive lifespan disrupts proper ovarian function.

Supported by R01 ES028661, R01 ES034112, T32 ES007326, and T32 HD10807