(99) Effects of Chronic Exposure to Diisononyl Phthalate (DINP) on the Female Reproductive Tract in Mice

Coba N. Sexton¹, Adriana R. Andrus¹, Lyda Y. Parra Forero¹, Kalysta C. Liu¹, Sarah M. Rush¹, Mary J. Laws², Jodi A. Flaws², Romana A. Nowak¹

¹Department of Animal Sciences, College of Agricultural, Consumer and Environmental Sciences, University of Illinois, Urbana, IL, USA; ²Department of Comparative Biosciences, College of Veterinary Medicine at the University of Illinois Urbana-Champaign (UIUC), Urbana, USA

Abstract Text:

Phthalates are a class of chemicals known for their endocrine-disrupting properties, including mimicking or antagonizing hormones and interfering with biological processes. Phthalates are commonly found in plastics, where they are used to improve flexibility and durability. Humans are subject to daily exposure to phthalates through ingestion, dermal contact, and inhalation in a variety of everyday products. Diisononyl Phthalate (DiNP) is becoming more commonly used as a substitute for di(2-ethylhexyl) phthalate (DEHP). The aim of this study was to determine how long term, chronic exposure to DiNP would affect uterine morphology, cell proliferation, inflammation and fibrosis related gene expression. Over a nine-month period, 40–45-day old CD-1 mice were fed chow containing 0.15 ppm DiNP, 1.5 ppm DiNP, or 1500 ppm of DiNP, or a vehicle control, daily. After the dosing period, the mice were euthanized in diestrus, and the uteri were collected for histology and RNA isolation. Fixed uterine tissues sections were stained with hematoxylin and eosin (H&E) to examine morphological changes. Immunohistochemistry was performed with the proliferation marker Ki67, the smooth muscle cell marker α-smooth muscle actin (αSMA), and the macrophage marker CD68. Analysis showed that chronic exposure to 1.5 ppm DiNP and 1500 ppm DiNP resulted in a significant increase in macrophages in the endometrium. No differences were seen in cell proliferation or myometrial morphology. Quantitative PCR was completed to determine changes in expression of genes associated with the inflammasome (IL18, IL1β, Nlrp3), inflammation (IL6 and IL10), fibrosis (TGFβ1, TGFβ3, COL1A1, COL3A1, COL4A1), and oxidative stress (Sod1, Cat, Gpx1, and Prdx2). Mice exposed to 1.5 ppm and 1500 ppm DiNP for nine months showed downregulation of the inflammasome gene IL1β. Significant upregulation of the inflammasome gene IL18, inflammation gene IL6, and fibrosis genes TGFβ3 and COL4A1 were seen only in the 1500 ppm DiNP dosage group. Downregulation of IL10 was seen in both the 0.15 ppm DiNP and 1500 ppm DiNP dosage groups. These results support that chronic exposure to DiNP can lead to increased chronic inflammation and fibrosis in the uterus. (Funded by NIH R01ES034112 to JAF, RAN).