Zelieann R Craig

Zelieann R Craig

Associate Professor, Animal and Comparative Biomedical Sciences
Assistant Dean, Research
Member of the Graduate Faculty
Associate Professor, BIO5 Institute
Department Affiliations
Contact
(520) 621-8082

Work Summary

We investigate how the chemicals in our daily lives interact with the female reproductive system and influence fertility. We hope that our discoveries will help reduce the incidence of infertility and improve women's health.

Research Interest

Nearly 50 million couples experience some form of infertility worldwide. Several factors increase a woman’s risk for infertility including aging, stress, and exposure to chemicals. A group of chemicals collectively known as phthalates have been classified as endocrine disruptors based on their ability to interact with the reproductive system. Phthalates have been detected in human urine, animal tissues, and feed. Despite these observations, how phthalates interact with the female reproductive system and what this means for overall fertility is currently unknown. Dr. Craig's work focuses on understanding how phthalates affect the function of the ovary, the major reproductive organ in females. Thus, work in her laboratory is focused on using animal models to help us understand the mechanisms by which phthalates exert their effects on the ovary, determine whether phthalates cause female infertility, and examine whether the effects of phthalates on female reproduction can be prevented or reversed. Using this knowledge she hopes to inspire and guide future work aimed at reducing, preventing, and/or reversing chemical-related infertility in humans and animals. Keywords: Infertility, Toxicology, Endocrine Disruptors, Phthalates, Reproduction

Publications

Craig, Z. R., Hannon, P. R., Wang, W., Ziv-Gal, A., & Flaws, J. A. (2013). Di-n-butyl phthalate disrupts the expression of genes involved in cell cycle and apoptotic pathways in mouse ovarian antral follicles. Biology of reproduction, 88(1), 23.

Di-n-butyl phthalate (DBP) is present in many consumer products, such as infant, beauty, and medical products. Several studies have shown that DBP causes reproductive toxicity in rodents, but no studies have evaluated its effects on ovarian follicles. Therefore, we used a follicle culture system to evaluate the effects of DBP on antral follicle growth, cell cycle and apoptosis gene expression, cell cycle staging, atresia, and 17β-estradiol (E(2)) production. Antral follicles were isolated from adult CD-1 mice and exposed to DBP at 1, 10, 100, and 1000 μg/ml for 24 or 168 h. Follicles treated with vehicle or DBP at 1-100 μg/ml grew over time, but DBP at 1000 μg/ml significantly suppressed follicle growth. Regardless of effect on follicle growth, DBP-treated follicles had decreased mRNA for cyclins D2, E1, A2, and B1 and increased p21. Levels of the proapoptotic genes Bax, Bad, and Bok were not altered by DBP treatment, but DBP 1000 μg/ml increased levels of Bid and decreased levels of the antiapoptotic gene Bcl2. DBP-treated follicles contained significantly more cells in G(1) phase, significantly less cells in S, and exhibited a trend for fewer cells in G(2). Although DBP did not affect E(2) production and atresia at 24 h, follicles treated with DBP had reduced levels of E(2) at 96 h and underwent atresia at 168 h. These data suggest that DBP targets antral follicles and alters the expression of cell cycle and apoptosis factors, causes cell cycle arrest, decreases E(2), and triggers atresia, depending on dose.

Wang, W., Craig, Z. R., Basavarajappa, M. S., Hafner, K. S., & Flaws, J. A. (2012). Mono-(2-ethylhexyl) phthalate induces oxidative stress and inhibits growth of mouse ovarian antral follicles. Biology of reproduction, 87(6), 152.

Mono-(2-ethylhexyl) phthalate (MEHP) is the active metabolite of the most commonly used plasticizer, di-(2-ethylhexyl) phthalate, and is considered to be a reproductive toxicant. However, little is known about the effects of MEHP on ovarian antral follicles. Thus, the present study tested the hypothesis that MEHP inhibits follicle growth via oxidative stress pathways. The data indicate that MEHP increases reactive oxygen species (ROS) levels and inhibits follicle growth in antral follicles, whereas N-acetylcysteine (NAC; an antioxidant) restores ROS levels to control levels and rescues follicles from MEHP-induced inhibition of follicle growth. To further analyze the mechanism by which MEHP induces oxidative stress and inhibits follicle growth, the expression and activities of various key antioxidant enzymes (copper/zinc superoxide dismutase [SOD1], glutathione peroxidase [GPX], and catalase [CAT]) and the expression of key cell-cycle regulators (Ccnd2, Ccne1, and Cdk4) and apoptotic regulators (Bcl-2 and Bax) were compared in control and MEHP-treated follicles. The data indicate that MEHP inhibits the expression and activities of SOD1 and GPX; does not inhibit Cat expression; inhibits the expression of Ccnd2, Ccne1, Cdk4, and Bcl-2; but increases the expression of Bax compared to controls. Furthermore, NAC blocks these toxic effects of MEHP. Collectively, these data suggest that MEHP induces oxidative stress by disrupting the activities of antioxidant enzymes. This may lead to decreased expression of cell-cycle regulators and antiapoptotic regulators and increased expression of proapoptotic factors, which then may lead to inhibition of follicle growth.

Basavarajappa, M. S., Craig, Z. R., Hernández-Ochoa, I., Paulose, T., Leslie, T. C., & Flaws, J. A. (2011). Methoxychlor reduces estradiol levels by altering steroidogenesis and metabolism in mouse antral follicles in vitro. Toxicology and applied pharmacology, 253(3), 161-9.

The organochlorine pesticide methoxychlor (MXC) is a known endocrine disruptor that affects adult rodent females by causing reduced fertility, persistent estrus, and ovarian atrophy. Since MXC is also known to target antral follicles, the major producer of sex steroids in the ovary, the present study was designed to test the hypothesis that MXC decreases estradiol (E₂) levels by altering steroidogenic and metabolic enzymes in the antral follicles. To test this hypothesis, antral follicles were isolated from CD-1 mouse ovaries and cultured with either dimethylsulfoxide (DMSO) or MXC. Follicle growth was measured every 24 h for 96 h. In addition, sex steroid hormone levels were measured using enzyme-linked immunosorbent assays (ELISA) and mRNA expression levels of steroidogenic enzymes as well as the E₂ metabolic enzyme Cyp1b1 were measured using qPCR. The results indicate that MXC decreased E₂, testosterone, androstenedione, and progesterone (P₄) levels compared to DMSO. In addition, MXC decreased expression of aromatase (Cyp19a1), 17β-hydroxysteroid dehydrogenase 1 (Hsd17b1), 17α-hydroxylase/17,20-lyase (Cyp17a1), 3β hydroxysteroid dehydrogenase 1 (Hsd3b1), cholesterol side-chain cleavage (Cyp11a1), steroid acute regulatory protein (Star), and increased expression of Cyp1b1 enzyme levels. Thus, these data suggest that MXC decreases steroidogenic enzyme levels, increases metabolic enzyme expression and this in turn leads to decreased sex steroid hormone levels.

Ziv-Gal, A., Craig, Z. R., Wang, W., & Flaws, J. A. (2013). Bisphenol A inhibits cultured mouse ovarian follicle growth partially via the aryl hydrocarbon receptor signaling pathway. Reproductive toxicology (Elmsford, N.Y.), 42, 58-67.

Bisphenol A (BPA) is an endocrine disruptor that inhibits growth of mouse ovarian follicles and disrupts steroidogenesis at a dose of 438μM. However, the effects of lower doses of BPA and its mechanism of action in ovarian follicles are unknown. We hypothesized that low doses of BPA inhibit follicular growth and decrease estradiol levels through the aryl hydrocarbon receptor (AHR) pathway. Antral follicles from wild-type and Ahr knock-out (AhrKO) mice were cultured for 96h. Follicle diameters and estradiol levels then were compared in wild-type and AhrKO follicles ± BPA (0.004-438μM). BPA inhibited follicle growth (110-438μM) and decreased estradiol levels (43.8-438μM) in wild-type and AhrKO follicles. However, at BPA 110μM, inhibition of growth in AhrKO follicles was attenuated compared to wild-type follicles. These data suggest that BPA may inhibit follicle growth partially via the AHR pathway, whereas its effects on estradiol synthesis likely involve other mechanisms.

Rasmussen, L. M., Sen, N., Liu, X., & Craig, Z. R. (2016). Effects of oral exposure to the phthalate substitute acetyl tributyl citrate on female reproduction in mice. Journal of applied toxicology : JAT.