Effects of Exposure <i>In Utero</i> to Bisphenol A on the Expression of Aryl Hydrocarbon Receptor, Related Factors, and Xenobiotic Metabolizing Enzymes in Murine Embryos

Abstract

Abstract.To evaluate the effects of bisphenol A (BPA), a candidate endocrine disruptor (ED), on embryonic development, we examined the mRNA expression levels of the aryl hydrocarbon receptor (AhR; which binds with many EDs and plays crucial roles in their metabolism) and related factors [aryl hydrocarbon receptor repressor (AhRR) and AhR nuclear translocator (Arnt)], xenobiotic metabolizing enzymes [XMEs; cytochrome P450 1A1 (CYP1A1) and UDP-glucuronosyltransferase, and the glutathione S-transferase Ya subunit (GST)], in murine embryos exposed in utero to BPA (0.02, 2, 200, and 20,000 µg/kg/day) and 17β-estradiol (E2; 5 µg/kg/day, used as a positive control) at 6.5-13.5 or 6.5-17.5 days post coitum (dpc) using the quantitative real-time reverse transcriptionpolymerase chain reaction (RT-PCR) method. Protein levels of CYP1A1 and GST in embryonic livers were estimated by Western immunoblotting. Exposure in utero to BPA [0.02 (1/100 dose of environmental exposure), 2, 200, and 20,000 µg/kg/day] increased AhR mRNA expression in the cerebra, cerebella, and gonads (testes and ovaries) of male and female mid-and late-developmental stage (14.5-and 18.5-dpc, respectively) embryos. BPA dose-independently up-regulated the expression of AhRR and Arnt in mid-and late-stage embryos. BPA had no remarkable effect on the mRNA levels of XMEs in mid-stage embryos, but dose-dependently up-regulated the expression in late-stage embryos. Moreover, the protein levels of these enzymes in the livers of late-stage embryos were increased. The present findings revealed that exposure to BPA in utero disrupts the expression of AhR and related factors and of xenobiotic metabolizing enzymes, and that mid-stage embryos, in the organogenic stage, are sensitive to BPA. Key words: Aryl hydrocarbon receptor (AhR), AhR relating factor, Bisphenol A (BPA), Murine embryo, Xenobiotic metabolizing enzymes (XMEs) (J. Reprod. Dev. 51: [593][594][595][596][597][598][599][600][601][602][603][604][605] 2005) isphenol A [BPA; 2,2-bis (4-hydroxyphenyl) propane], which is composed of two benzene rings and in conformation resembles a synthetic estrogen, diethylstilbestrol (DES), is a common plasticizer for polycarbonate and epoxy resins and a candidate environmental endocrine disruptor (ED) [1,2]. BPA has toxicological effects on the reproductive, immunological, and nervous systems in mammals, binds with estrogen receptor-α (ERα; NR3A1) and ER-β (NR3A2), and induces estrogenic activity [3][4][5][6]. BPA affects the expression levels of ERs and ER-like nuclear receptor mRNAs in the rat uterus [6], but the mechanism of its actions has yet

Biomarkers for exposure to estrogenic compounds: Gene expression analysis in zebrafish (Danio rerio)

“…It has already been shown that BPA can be found in the human amniotic fluid (Tsutsumi, 2005). This documents that humans can be exposed to this substance and that this chemical is able to alter human gene expression patterns was shown by Nishizawa et al (2005).…”

Effects of Vertically Transferred 3,3',4,4',5-Pentachlorobiphenyl (PCB-126) on the Reproductive Development of Female Rats

“…Real-time RT-PCR revealed that the ovary was equipped with AhRsignaling molecules, such as AhR and ARNT, and that CYP1A1 mRNA was induced in the PCB-126 exposed groups. It has been shown that prenatal exposure to estrogen or an extremely high dose of an estrogenic environmental contaminant, bisphenol A, also induces CYP1A1 mRNA in midor late gestational murine embryos [10]. However, the authors found that the treatment did not affect the CYP1A1 mRNA levels in the ovary.…”

NTP‐CERHR expert panel report on the reproductive and developmental toxicity of bisphenol A

“…Nishizawa et al (2005a), supported by the Japan Society for the Promotion of Science, examined the effects of bisphenol A exposure on expression of aryl hydrocarbon receptors, related factors, and metabolizing enzymes in mouse embryos. ICR mice were fed standard diet (CM; Oriental Yeast).…”

“…Other endpoints: Following oral exposure of mice to bisphenol A during gestation, changes were observed for mRNA expression of arylhydrocarbon receptors, receptor repressor, or nuclear translocator and retinoic acid and retinoid X receptors in brain, testes, and/or ovary at 0.00002-20 mg/kg bw/day (Nishizawa et al, , 2005a. The strongest effects were found at the lowest doses following exposures during organogenesis (GD 6.5-13.5 or 6.5-17.5) (Nishizawa et al, 2005a,b).…”

“…2.5 mg/kg/day, gestation and lactation in rats, (Funabashi et al, 2004a); LOEL 0.00002 mg/kg/day, fetal mice, (Nishizawa et al, 2005a); 0.0002 mg/kg/day, fetal mice, , 0.04 mg/kg/day, weaning to puberty, rats, (Ceccarelli et al, 2007); 0.1 mg/kg/day, GD 3-PND 20, rats, (Negishi et al, 2004a); 0.2 mg/kg/ day, GD 3-PND 20, mice, (Ryan and Vandenbergh, 2006); 0.01 mg/kg/day, GD 11-18, mice, , although other studies report no change in a related measure, the size of the sexually dimorphic nucleus of the pre-optic area (SDN-POA) [300 mg/kg/day, rats (Nagao et al, 1999); NOEL of 320 mg/kg/day, rats, (Kwon et al, 2000)]. …”