Estrogen receptor alpha mediates 17 alpha-ethynylestradiol causing hepatotoxicity
ABSTRACT Estrogens are known to cause hepatotoxicity such as intrahepatic cholestasis in susceptible women during pregnancy, after administration of oral contraceptives, or during postmenopausal replacement therapy. Enterohepatic nuclear receptors including farnesoid X receptor (FXR), pregnane X receptor (PXR), and constitutive active/androstane receptor (CAR) are important in maintaining bile acid homeostasis and protecting the liver from bile acid toxicity. However, no nuclear receptor has been implicated in the mechanism for estrogen-induced hepatotoxicity. Here Era(-/-), Erb(-/-), Fxr(-/-), Pxr(-/-), and Car(-/-) mice were employed to show that Era(-/-) mice were resistant to synthetic estrogen 17alpha-ethynylestradiol (EE2)-induced hepatotoxicity as indicated by the fact that the EE2-treated Era(-/-) mice developed none of the hepatotoxic phenotypes such as hepatomegaly, elevation in serum bile acids, increase of alkaline phosphatase activity, liver degeneration, and inflammation. Upon EE2 treatment, estrogen receptor alpha (ERalpha) repressed the expression of bile acid and cholesterol transporters (bile salt export pump (BSEP), Na(+)/taurocholate cotransporting polypeptide (NTCP), OATP1, OATP2, ABCG5, and ABCG8) in the liver. Consistently, biliary secretions of both bile acids and cholesterol were markedly decreased in EE2-treated wild-type mice but not in the EE2-treated Era(-/-) mice. In addition, ERalpha up-regulated the expression of CYP7B1 and down-regulated the CYP7A1 and CYP8B1, shifting bile acid synthesis toward the acidic pathway to increase the serum level of beta-muricholic acid. ERbeta, FXR, PXR, and CAR were not involved in regulating the expression of bile acid transporter and biosynthesis enzyme genes following EE2 exposure. Taken together, these results suggest that ERalpha-mediated repression of hepatic transporters and alterations of bile acid biosynthesis may contribute to development of the EE2-induced hepatotoxicity.
- SourceAvailable from: María L Ruiz
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- "The volume of distribution for EE in rats was estimated to be 2 l/kg (Zamek- Gliszczynski et al., 2011), and in consequence, a concentration of EE of 10 mM would be compatible with administration of a 5–6 mg/kg birth weight dose of EE, which is equivalent to the single dose currently administered in vivo. ER-a was also implicated in repression of hepatic transporters and alteration of bile acid biosynthesis using a dose of EE that is even higher than the dose commonly used in rats (Yamamoto et al., 2006). Although the observed increase in mRNA levels after 5 hours of treatment in vivo and in hepatocytes might be caused by ER as a common mediator, further studies would be necessary to demonstrate that the increased Mrp3 mRNA levels occurring in the isolated hepatocytes model results in induction of Mrp3 protein, as previously seen after repeated treatment in vivo (Ruiz et al., 2007). "
ABSTRACT: Multidrug resistance-associated protein 3 (Mrp3; Abcc3) expression and activity are up-regulated in rat liver after in vivo repeated administration of ethynylestradiol (EE), a cholestatic synthetic estrogen, whereas Mrp2 is down-regulated. This study was undertaken to determine if Mrp3 induction results from a direct effect of EE, independent of accumulation of any endogenous common Mrp2/Mrp3 substrates resulting from cholestasis, and the potential mediation of estrogen receptor (ER). In in vivo studies, male rats were given a single, non-cholestatic, dose of EE (5 mg/Kg, s.c.) and basal bile flow and the biliary excretion rate of bile salts and glutathione measured 5 h later. This treatment increased Mrp3 mRNA 4-fold, detected by real time PCR, despite the absence of cholestasis. Primary culture of rat hepatocytes incubated with EE (1-10 μM) for 5 h, exhibited a 3-fold increase in Mrp3 mRNA (10 μM), consistent with in vivo findings. The increase in Mrp3 mRNA by EE was prevented by actinomycin D, indicating transcriptional regulation. When hepatocytes were pre-incubated for 30 min with an estrogen receptor antagonist (ICI182/780, 1 μM) before the addition of EE, induction of Mrp3 mRNA was abolished, implicating ER as a key mediator. EE induced an increase in ER-α phosphorylation at 30 min, as detected by Western blotting in nuclear extracts. This increase was prevented by ICI182/780. In summary, EE increased the expression of hepatic Mrp3 transcriptionally and independently of any cholestatic manifestation, and required participation of an ER, most likely ER-α, through its phosphorylation.Drug metabolism and disposition: the biological fate of chemicals 10/2012; 41(2). DOI:10.1124/dmd.112.047357 · 3.33 Impact Factor
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- "They were ovariectomized at 5–7 weeks of age, and a week later they were injected i.p. two times, 24 h apart, with one of the following treatments: 1 mg b-estradiol (nZ3), 50 mg b-estradiol (nZ5), 50 mg MPP (nZ3), 50 mg raloxifene (nZ3), 50 mg ICI 182 780 (nZ3), 50 mg b-estradiol C50 mg MPP (nZ3), 50 mg b-estradiol C50 mg raloxifene (nZ3), 50 mg b-estradiol C50 mg ICI 182 780 (nZ5), and DMSO vehicle control (nZ3). These doses were chosen based on past studies that tested the effects of b-estradiol and SERMs in mice (Jones & Bern 1977, Carthew et al. 1999, Gutman et al. 2002, Hewitt et al. 2003, McDougall et al. 2003, Chin et al. 2005, Davis et al. 2006, Hatsumi & Yamamuro 2006, Yamamoto et al. 2006, Chen et al. 2007, Glidewell-Kenney et al. 2007, Gresack et al. 2007, Thakur & Sharma 2007). "
ABSTRACT: Selective estrogen receptor modulators (SERMs) are potentially useful in treating various endometrial disorders, including endometrial cancer, as they block some of the detrimental effects of estrogen. It remains unclear whether each SERM regulates a unique subset of genes and, if so, whether the combination of a SERM and 17beta-estradiol has an additive or synergistic effect on gene expression. We performed microarray analysis with Affymetrix Mouse Genome 430 2.0 short oligomer arrays to determine gene expression changes in uteri of ovariectomized mice treated with estradiol (low and high dose), methyl-piperidino-pyrazole (MPP), ICI 182 780, raloxifene, and combinations of high dose of estradiol with one of the SERM and dimethyl sulfoxide (DMSO) vehicle control. The nine treatments clustered into two groups, with MPP, raloxifene, and high dose of estradiol in one, and low dose of estradiol, ICI + estradiol, ICI, MPP + estradiol, and raloxifene + estradiol in the second group. Surprisingly, combining a high dose of estradiol with a SERM markedly increased (P<0.02) the number of regulated genes compared with each individual treatment. Analysis of expression for selected genes in uteri of estradiol and SERM-treated mice by quantitative (Q)RT-PCR generally supported the microarray results. For some cancer-associated genes, including Klk1, Ihh, Cdc45l, and Cdca8, administration of MPP or raloxifene with estradiol resulted in greater expression than estradiol alone (P<0.05). By contrast, ICI 182 780 suppressed more genes governing DNA replication compared with MPP and raloxifene treatments. Therefore, ICI 182 780 might be superior to MPP and raloxifene to treat estrogen-induced endometrial cancer in women.Journal of Molecular Endocrinology 10/2008; 41(4):205-17. DOI:10.1677/JME-08-0029 · 3.62 Impact Factor
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ABSTRACT: Alterations in hepatic lipid profiles of fathead minnows (FHM) exposed to the synthetic estrogen 17α-ethynylestradiol (EE2) were determined using 1H-NMR spectroscopy-based metabolite profiling. The exposures were conducted using either 10ng/l or 100ng/l EE2 via a continuous flow water delivery system. Livers were collected at 1, 4, and 8days of the exposure and 8days after the chemical was removed from the water (i.e. an 8day depuration). The exposure resulted in a number of sex-specific changes in lipid profiles that were also highly time dependent. Those metabolites most affected by exposure included phosphatidylcholine, diglycerides, triglycerides and cholesterol. In addition, changes in the length and degree of unsaturation of hepatic fatty acids were observed. Lipid profiles in plasma for fish collected on the 4th day of exposure were also analyzed in order to provide further insights into changes observed in hepatic metabolite changes. Using validated partial least-squares discriminant analysis (PLS-DA), the response trajectories of the male liver lipid profiles at both exposure concentrations were compared. This analysis indicated that the males exposed to the low concentration of EE2 (10ng/l) were largely able to recover from the exposure once the chemical was removed from the water. Conversely, the males exposed to the high concentration (100ng/l) did not appear to recover from the exposure despite the 8day depuration.Metabolomics 03/2008; 5(1):22-32. DOI:10.1007/s11306-008-0138-y · 3.97 Impact Factor