Independent and combined effects of Bisphenol A and Diethylhexyl Phthalate on gestational outcomes and offspring development in Sprague-Dawley rats
Introduction
Increased prevalence of human health risks has been correlated with environmental contaminants, including the plastic-derived compounds: Bisphenol-A (BPA) and Di-2-ethylhexyl phthalate (DEHP). BPA is a weak estrogen while DEHP has anti-androgenic properties. They interfere with the endocrine system by activating a broad range of signaling pathways (Gould et al., 1998; Grun and Blumberg, 2006; Latini et al., 2004). BPA and DEHP are ubiquitously present in the environment. They are extensively used in a variety of consumer products including plastic bottles, dental fillings and sealants, eyeglass lenses, sports equipment, household electronics and food packaging (Hashimoto and Nakamura, 2000; Yoshida et al., 2001). Exposure to these chemicals occurs through ingestion of contaminated food or water, inhalation of contaminated air and dust, and dermal absorption (Hernandez-Diaz et al., 2009; Erythropel et al., 2014; Diamanti-Kandarakis et al., 2009; Morgan et al., 2018). BPA and DEHP can leach into the environment from plastic products as they degrade over time and increase human exposures (Erythropel et al., 2014; Yoshida et al., 2001; Yamamoto and Yasuhara, 1999).
The prevalence of BPA and DEHP in the environment has raised concerns, in particular because they have been detected in the serum (Schonfelder et al., 2002), amniotic fluid (Jensen et al., 2012; Calafat et al., 2006; Edlow et al., 2012; Ikezuki et al., 2002), placental tissue (Schonfelder et al., 2002; Jimenez-Diaz et al., 2010) and fetal serum (Talsness et al., 2009; Troisi et al., 2014; Schonfelder et al., 2002; Ikezuki et al., 2002). This implies that BPA and DEHP can cross the placenta during the critical periods of development and program the fetus for possible adult-onset disorders (Liu et al., 2013).
Animal and human studies have demonstrated some of the permanent and irreversible in utero effects of low-dose BPA and DEHP on different organ systems (Colborn, vom Saal, and Soto, 1993) (vom Saal et al., 1998; Hatch et al., 2010; Naville et al., 2013). Early life exposure to DEHP is associated with a decrease in pregnancy weight gain (Gray et al., 2000), fetal growth (Ferguson et al., 2016), pup weight at birth (Gray et al., 2000) and anogenital distance in male infants (Swan et al., 2005; Gray et al., 2000) (Parks et al., 2000). In utero exposure to BPA is shown to produce sex-specific reductions in offspring birth weight (Huo et al., 2015), increase in gestational length (Veiga-Lopez et al., 2015), and shortened anogenital distance in male offspring (Sun et al., 2018). Besides, exposure to environmentally relevant low doses BPA and DEHP have been linked to a number of chronic diseases including metabolic, reproductive, cardiovascular, and neurological disorders (De Coster and van Larebeke, 2012; Rochester, 2013; Richter et al., 2007; Vandenberg et al., 2009; Rubin and Soto, 2009; Rubin, 2011; Lyche et al., 2009). However, the effects of prenatal exposures to a mixture of low doses of these chemicals have not been studied.
This study aimed to investigate the effects of prenatal exposure to a mixture of low dose BPA and DEHP on Sprague Dawley rat development, as well as the sex differences in their biological effects. We used a single low dose of BPA (5 μg/kg BW) in combination with either a low dose (5 μg/kg BW) of DEHP to match the BPA dose or a higher dose (7.5 mg/kg BW) based on earlier studies (Rattan et al., 2018; Tinwell et al., 2002). Exposures were limited to the prenatal period (gestational days 6–21). We hypothesized that prenatal exposure to EDCs will “program” the offspring and affect their postnatal morphometric parameters, body weights, and organ weights in a sex-specific manner with the EDC mixture showing a more pronounced effect than individual EDCs.
Section snippets
Chemicals
BPA (Lot # MKBH2096V) and DEHP (Lot # BCBR8079V) were purchased from Sigma Aldrich (St. Louis, MO). Stock solutions of BPA and DEHP were made in DMSO and diluted with saline prior to oral administration. Pregnant dams were administered BPA (5 μg/kg BW), low dose (LD) DEHP (5 μg/kg BW), high dose (HD) DEHP (7.5 mg/kg BW) or a combination of BPA with either dose of DEHP (As summarized in Fig. 1). Animals were dosed from gestational days (GD) 6–21. The dosing volume was adjusted based on
Effect of in utero BPA and DEHP exposure on gestational parameters
Pregnancy outcomes are outlined in Table 1 and Fig. 2 (A). There were no significant differences in percent gestational weight gain between pregnant dams from different treatment groups. However, the reproductive outcome was impaired in dams exposed to DEHP and BPA + DEHP. Dams exposed to BPA or LD-D had no abortion and were comparable to control rats. In contrast, exposure to HD-D induced abortions in 9% of the dams. Exposure to BPA + LD-D increased the abortion rate to 14%, and exposure to
Discussion
Previous studies have identified BPA and DEHP independently as reproductive (Shi et al., 2019, 2019b), developmental, and systemic toxicants (Naule et al., 2014) (Tyl et al., 2008; Shi et al., 2019). However, studies investigating the effects of BPA and DEHP mixtures are few. Exposure to EDC mixtures is probably more common rather than exposure to any individual EDC due to their ubiquitous presence in the environment. Moreover, both BPA and DEHP metabolites have been found in the urine of
Credit author statement
Josephine Bou Dagher: Investigation, Formal analysis, visualization, writing original draft. Coral K. Hahn-Townsend: Investigation, formal analysis, visualization. Amrita Kaimal: Investigation, formal analysis. Maryam Al Mansi: Investigation, data curation, validation. Joseph E. Henriquez: Investigation, formal analysis. Diane G. Tran: Investigation, data curation, visualization. Christian R. Laurent: Investigation, data curation, visualization. Caleb J. Bacak: Investigation, data curation.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by MSU (Michigan State University) Ag BioResearch USDA 0210553 and startup funds from the University of Georgia. We thank Dr. Vasantha Padmanabhan for initiating the conversation on EDC mixtures in our laboratory.
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