The aryl hydrocarbon signaling pathway in the ovary changes throughout reproductive aging and in response to a mixture of phthalates over time in mice.

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 ppm, 1.5 ppm, or 1500 ppm) of Mix for 1-12 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 PCR (qPCR) for gene expression, RNAscopeTM 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 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 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.