Exposure to di(2-ethylhexyl) phthalate and diisononyl phthalate alters the aryl hydrocarbon receptor signaling pathway in the ovary throughout reproductive aging in mice.

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 1500 ppm) of DEHP and DiNP in the diet for 1-12 months. Sera were used to measure circulating estradiol (E2) concentrations. The AHR pathway was assessed using quantitative PCR (qPCR) for gene expression, RNAscopeTM in situ hybridization for transcript localization, and immunohistochemistry for protein localization. Exposure to DEHP, but not DiNP, reduced serum E2 after 1 month compared to control. DEHP exposure increased Cyp1a1 expression and CYP1B1 localization in the ovary after 6 months compared to control. DiNP also increased Arnt expression and CYP1B1 localization in the ovary after 1 month compared to control. DiNP exposure decreased Ahr and Cyp1a1 expression as well as CYP1A1 localization in the antral follicle after 12 months compared to control. Overall, DEHP and DiNP both influence the ovarian AHR pathway, but at different time points and doses.