Decreased, Chicken Ovalbumin Upstream Promoter Transcription Factor II (COUP-TFII) leads to Impaired, Spermatogenesis

Of the originating work: Christine M. Palermo and Jennifer E. Foreman, ExxonMobile; Daniele S. Wikoff, Isabel Lea, ToxStrategies.

Of the content populated in the AOP-Wiki:  John R. Frisch and Travis Karschnik, General Dynamics Information Technology; Daniel L. Villeneuve, US Environmental Protection Agency, Great Lakes Toxicology and Ecology Division.  

Impaired spermatogenesis is an adverse outcome often observed among a group of male reproductive abnormalities caused by organ malformation (epididymis, vas deferens, seminal vesicles, prostate, external genitalia) during development (Drake et al. 2009; Palermo et al. 2021).  These reproductive abnormalities have been observed in studies of laboratory mice and rats exposed to phthalates during in utero development, in attempts to understand the gene expression/inhibition, hormone levels, and other factors leading to the observed adverse outcomes.  Studies in laboratory mammals have allowed researchers to target the role of individual genes by knockout gene studies, and target critical developmental windows by timed exposure to toxicants, to explore the mechanisms leading to reproductive defects similar to human birth defects observed in clinical studies (Review in Foster 2006).  Although a molecular initiating event isn’t well established, decreased Chicken Ovalbumin Upstream Promoter Transcription Factor II (COUP-TFII)) gene expression has been linked to decreased expression of genes coding for enzymes involved in steroidogenesis and decreased testosterone levels in mammals (Qin et al. 2008; van den Driesche et al. 2012; Mendoza-Villarroel et al. 2014).  One adverse outcome of decreased testosterone, and the focus of this adverse outcome pathway, is epididymal agenesis, and resulting impaired spermatogenesis (Mahood et al. 2007; Qin et al. 2008; Kim et al. 2010).  Impaired spermatogenesis results in decreased sperm counts, as well as decreases in the number of sperm capable of fertilization (Barlow and Foster 2003).

This Adverse Outcome Pathway (AOP) was developed as part of an Environmental Protection Agency effort to represent putative AOPs from peer-reviewed literature which were heretofore unrepresented in the AOP-Wiki.  The originating work for this AOP was: Palermo, C.M., Foreman, J.E., Wikoff, D.S., and Lea, I.  2021.  Development of a putative adverse outcome pathway network for male rat reproductive tract abnormalities with specific considerations for the androgen sensitive window of development.  Current Research in Toxicology 2: 254–271.  This publication, and the work cited within, were used create and support this AOP and its respective KE and KER pages. 

Phthalates are of increasing human health concern because of increased use and accumulating evidence of disruption of reproductive development in vertebrates.  First detected in laboratory mammals, exposure to phthalates and other toxicants in utero when male sexual differentiation is occurring have resulted in increased malformation of reproductive organs, failure of male characteristics to develop, and failure of proper positioning of organs (ex. hypospadias and cryptorchidism).  Clinical studies in humans have used laboratory mammal data to help understand and treat conditions exhibited by individual people.   This AOP focuses on the pathway leading to impaired to spermatogenesis, via abnormal formation of the epididymis, decreased testosterone levels, and initiated by decreased Chicken Ovalbumin Upstream Promoter Transcription Factor II (COUP-TFII) gene expression and subsequent disrupted signaling for steroidogenesis.

The focus of the originating work was to use an AOP framework to integrate lines of evidence from multiple disciplines based on evolving guidance developed by the Organization for Economic Cooperation and Development (OECD).  Palermo et al. (2021) provided network analysis based on two literature searches: 1. rodent male reproductive development abnormalities using key terms; 2. effects of low molecular weight phthalates (LMWPs) during the rodent male programming window (MPW) of development.  Relevant key events and key event relationships were narrowed by focusing on empirical studies related to ‘rat phthalate syndrome’ which resulted in 3 recommended Adverse Outcome Pathways: 1. INSL expression to cryptorchidism (see AOP 528 for related content); 2. COUP-TFII expression to hypospadias (see AOP 527 for related content); 3. COUP-TFII expression to altered sperm maturation (see this AOP 526 for related content).  

The originating authors conducted a literature search to develop a database of publications categorized by discipline or field of study: toxicology, epidemiology, exposure, and gene-environment interaction. The literature search relied on standard search engines such as Web of Science and Google Scholar, and the search strategy focused on toxicants known to disrupt lipid pathways in organisms, and diet studies with elevated levels of lipids. The originating authors reviewed references from individual citations to identify additional studies not captured through the literature search itself. They then included all relevant publications through 2023. Only studies focused primarily on developmental or neurotoxic endpoints were included; those focused on carcinogenesis or other systemic effects were not included unless there was a particular relevance to a neurotoxic or developmental outcome.

The scope of the aforementioned EPA project was limited to re-representing the AOP(s) as presented in the originating publication. The literature used to support this AOP and its constituent pages began with the originating publication and followed to the primary, secondary, and tertiary works cited therein. KE and KER page creation and re-use was determined using Handbook principles where page re-use was preferred.  

The authors of AOP 526 also referred to existing AOP-wiki content on disruption of steroidogenesis pathways, especially work by Gary Klinefelter (ex. AOP 70, 71).  We found existing Adverse Outcome Pathway content documented different series of key events then the pathways provided by Palermo et al. (2021), and therefore initiated AOP 526 and updated existing AOP-wiki key events when available.  

Barlow, N.J. and Foster, P.M.D.  2003.  Pathogenesis of Male Reproductive Tract Lesions from Gestation Through Adulthood Following in Utero Exposure to Di(n-butyl) Phthalate.  Toxicologic Pathology 31:397–410.

Drake, A.J., van den Driesche, S., Scott, H.M., Hutchinson, G.R., Seckl, J.R. and Sharpe, R.M.  2009.  Glucocorticoids Amplify Dibutyl Phthalate-Induced Disruption of Testosterone Production and Male Reproductive Development.  Endocrinology 150(11): 5055–5064.

Foster, P.M.D.  2006. Disruption of reproductive development in male rat offspring following in utero exposure to phthalate esters.  International Journal of Andrology 29: 140–147.

Kim, T.S., Jung, K.K., Kim, S.S., Kang, I.H., Baek, J.H., Nam, H.-S., Hong, S.-K., Lee, B.M., Hong, J.T., Oh, K.W., Kim, H.S., Han, S.Y., and Kang, T.S.  2010.  Effects of in Utero Exposure to DI(n-Butyl) Phthalate on Development of Male Reproductive Tracts in Sprague-Dawley Rats.  Journal of Toxicology and Environmental Health, Part A 73(21-22): 1544-1559.

Mahood, I.K., Scott, H.M., Brown, R., Hallmark, N., Walker, M., and Sharpe, R.M.  2007.  In Utero Exposure to Di(n-butyl) Phthalate and Testicular Dysgenesis: Comparison of Fetal and Adult End Points and Their Dose Sensitivity.  Environmental Health Perspectives 115 (supplement 1): 55-61.

Mendoza-Villarroel, R.E., Robert, N.M., Martin, L.J., Brousseau, C., and Tremblay, J.J.  2014.  The Nuclear Receptor NR2F2 Activates Star Expression and Steroidogenesis in Mouse MA-10 and MLTC-1 Leydig Cells.  Biology of Reproduction 91(1) Article 26: 1-12.

Palermo, C.M., Foreman, J.E., Wikoff, D.S., and Lea, I.  2021.  Development of a putative adverse outcome pathway network for male rat reproductive tract abnormalities with specific considerations for the androgen sensitive window of development.  Current Research in Toxicology 2: 254–271.

Qin, J., Tsai, M.-J., and Tsai S.Y.  2008.  Essential Roles of COUP-TFII in Leydig Cell Differentiation and Male Fertility.  Public Library of Science One 3(9): e3285.

van den Driesche, S., Walker, M., McKinnel, C., Scott, HM., Eddie, S.L., Mitchell, R.T., Seckl, J.R., Drake, A.J., Smith, L.B., Anderson, R.A., and Sharpe, R.M.  2012.  Proposed Role for COUP-TFII in Regulating Fetal Leydig Cell Steroidogenesis, Perturbation of Which Leads to Masculinization Disorders in Rodents. Public Library of Science One 7(5): e37064.