Developmental exposure to an environmentally relevant phthalate mixture impacts ovarian health in mice

Fletcher, Endia J.

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https://hdl.handle.net/2142/129503 Copy

Description

Title

Developmental exposure to an environmentally relevant phthalate mixture impacts ovarian health in mice

Author(s)

Fletcher, Endia J.

Issue Date

2025-03-25

Director of Research (if dissertation) or Advisor (if thesis)

Flaws , Jodi

Doctoral Committee Chair(s)

Flaws , Jodi

Committee Member(s)

• Boppart, Stephen
• Mahoney, Megan
• Reddi, Prabhakara

Department of Study

Comparative Biosciences

Discipline

VMS - Comparative Biosciences

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Ovary
• inflammation
• toxicology
• female reproductive toxicity
• phthalates
• prenatal exposure
• neonatal exposure
• apoptosis
• developmental exposure
• developmental origins of health and diseases (DoHAD)

Abstract

Phthalates are a group of synthetic chemical compounds used as plasticizers. Phthalates are widely used in consumer products such as children’s toys, medical tubing, food and beverage packaging, cosmetics, and many other items containing plastics. Phthalates are non-covalently bound in plastics and, therefore, have the potential to leach out of plastics when exposed to high temperatures, aging, and cleaning products. Humans are exposed to phthalates daily via ingestion, dermal absorption, inhalation, and parenteral administration. Phthalates are primarily absorbed via ingestion and have been classified as endocrine-disrupting chemicals. Studies have shown that women are more likely to be exposed to higher amounts of phthalates than men, which raises a public health concern about the impact of phthalate exposure on female reproductive health. Women are likely to be exposed to phthalates throughout their entire reproductive lifespan, starting in utero and following into late adulthood. The female reproductive system relies heavily on the development and function of the ovary. In mammals, in-utero and neonatal development are considered two highly sensitive periods, which are critical for the healthy development of the ovary. Exposure to chemicals such as phthalates can interrupt normal development, causing long-term impacts on female reproductive health. Previous studies indicate that phthalates can impact female reproductive health by altering hormone production, estrous cyclicity, folliculogenesis, sexual growth, sexual development, and fertility. Phthalates have been increasingly studied over the last decade. However, most previous research focused on the effects of single phthalate exposure on female reproductive health, whereas phthalates are prevalent in the environment as mixtures. Limited research exists on the impacts of developmental exposure to phthalates on female reproductive health and its potential mechanisms. Inflammation, apoptosis, cell cycle inhibition, and oxidative stress are well-characterized mechanisms associated with negative female reproductive outcomes. Thus, this dissertation research was designed to test a series of hypotheses on the common mechanisms by which developmental exposure to phthalate mixtures impacts ovarian function in female mice. First, this research tested the hypothesis that prenatal exposure to an environmentally relevant phthalate mixture alters serum cytokine levels and inflammatory markers in F1 mouse ovaries. Specifically, the research was designed to evaluate the levels of C-reactive protein (CRP), a known pro-inflammatory marker, and measured ovarian gene expression of pro- and anti-inflammatory cytokines found within the mouse ovary. The research was also designed to use cytokine arrays to detect major cytokines, chemokines, and growth factors known to impact inflammation in the ovary and sera. The results indicate that prenatal exposure to a phthalate mixture interferes with the immune response in F1 female mice long after initial exposure by significantly increasing CRP levels within the sera at postnatal day (PND) 21 and altering the levels of six other major inflammatory markers. The result also indicate that the phthalate mixture altered 33 immune factors in the ovary and sera at 6 months compared to controls. Overall, the data indicate that prenatal exposure to an environmentally relevant phthalate mixture may dysregulate immune response entirely in F1 female mice. Second, this dissertation research was designed to test the hypothesis that prenatal exposure to an environmentally relevant phthalate mixture alters oxidative stress, apoptosis, cell cycle regulators, and steroidogenic factors in F1 female mice. Ovaries were used to evaluate the proliferative marker, Ki67, and to quantify the gene expression of steroidogenic regulators, antioxidant enzymes, apoptotic factors, and cell cycle regulators. Sera were also used to measure sex steroid hormone levels. The results indicate that exposure to the phthalate mixture disrupted gene expression of many steroidogenic regulators and apoptotic factors at PND 60, 3 months, and 6 months and caused a decrease in testosterone levels in female mice at 6 months in comparison to controls. Lastly, this dissertation research was designed to the hypothesis that short-term neonatal exposure to an environmentally relevant phthalate mixture impacts early ovarian development through the promotion of inflammation, oxidative stress, apoptosis, and cell cycle arrest in female mice. Ovaries were used to count follicle types and quantify gene expression of steroidogenic regulators, antioxidant enzymes, apoptotic factors, cell cycle regulators, and inflammation markers. Sera were used to determine the phthalate metabolite levels. Neonatal weights were also recorded over the duration of the study. The results indicate that neonatal exposure to the mixture altered primordial follicle numbers, increased levels of CRP, and altered gene expression of oxidative stress, apoptotic, and steroidogenic markers in comparison to controls. The data also demonstrated that neonatal mice are capable of absorbing the parent phthalates and converting them into their respective phthalate metabolites. Further, these data indicate that neonatal exposure to the mixture significantly altered gene expression steroidogenic regulators, apoptotic factors, and cell cycle regulators within the ovaries at PND 10. Collectively, these experiments from my doctoral studies show that developmental exposure to phthalate mixture can have short and long-term consequences on ovarian function through the dysregulation of immune signaling, apoptotic factors, oxidative stress markers, and cell cycle regulators.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129503

Copyright and License Information

Chapters 2-4 were reprinted with permission from contributing co-authors within the journals of Toxics, Toxicological Science, and Reproductive Toxicology.

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