(108) Di(2- ethylhexyl) Phthalate and  Diisononyl Phthalate Exposure Alters Hox Gene Expression in the Ovary

Mary J. Laws, Teegan Gonyea, Lindsey Edwards, Catheryne Chiang, Jodi A. Flaws

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

Abstract Text:

Phthalates are a class of environmental contaminants found in plastic food containers, medical plastics, and personal care products. Di(2- ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DiNP) are two of the most widely used phthalates globally. Because phthalates leach from plastics, humans are continuously exposed to these toxicants. According to the National Health and Nutrition Examination Survey, the majority of the US population is exposed to phthalates. Studies have shown that phthalate exposure negatively affects female reproductive health. However, the effects of DEHP and DiNP exposure on the ovary are largely unknown.  Thus, this study investigated the effects of phthalate exposure on global ovarian gene expression in female mice. Adult female CD-1 mice were dosed with either vehicle control, DEHP (20 μg/kg/day and 200 µg/kg/day), or DiNP (20 μg/kg/day and 100 µg/kg/day) for 10 days. These phthalate dose concentrations represent levels of daily human exposure. Measurements of urinary phthalate metabolites confirmed effective delivery of phthalates. Further, phthalate metabolites were detected in ovarian tissue. To assess ovarian expression with an unbiased approach, RNA sequencing determined differentially expressed genes (DEGs) in the ovaries of control and phthalate treated mice.  These results indicated that 360 genes were differentially expressed between 20 µg/kg DEHP ovaries and vehicle control, and 876 genes were differentially expressed between 200 µg/kg DEHP ovaries and vehicle control. DEHP (20 µg/kg and 200 µg/kg) treatment groups had 111 DEGs in common compared to vehicle control. Some common KEGG pathways between 20 µg/kg and 200 µg/kg DEHP exposure were ‘cytokine-cytokine receptor interaction’, ‘transcriptional misregulation in cancer,’ ‘hematopoietic cell lineage,’ and ‘insulin secretion.’ The results indicated that 312 genes were differentially regulated between 20 µg/kg DiNP ovaries and vehicle control, and 278 genes differentially regulated between 100 µg/kg DiNP ovaries and vehicle control. DiNP (20 µg/kg and 100 µg/kg) treatment groups had 95 DEGs in common when compared to vehicle control ovaries. Some common KEGG pathways between 20 µg/kg and 100 µg/kg DiNP exposure were ‘protein processing in endoplasmic reticulum’ and ‘Jak-STAT signaling pathway.’ Among all four treatment groups, 19 DEGs were found in common when compared to vehicle control. Of the 19 common DEGs, three genes belonged to the Hox family of transcription factors: Hoxb3, Hoxc10, and Hoxd10. Investigation of Hox genes by quantitative polymerase chain reaction revealed the following Hox genes to be differentially regulated between at least one phthalate treatment group and vehicle control: Hoxb2, Hoxb7, Hoxb3os, and Hoxd11. These data indicate DEHP and DiNP exposure aberrantly regulate ovarian gene expression. Further, DEHP and DiNP exposure may negatively impact ovarian health by affecting the Hox family of transcription factors. Supported by NIH R01 ES032163, NIH R01 ES034112, and NIH T32ES007326.