An Evaluation of Estrogenic Activity of Parabens Using Uterine Calbindin-D9k Gene in an Immature Rat Model

Toxicological Sciences, Nov 2009

In the present study, calbindin-D9k (CaBP-9k), a potent biomarker for screening estrogen-like environmental chemicals in vivo and in vitro, was adopted to examine the potential estrogen-like property of the following parabens: propyl-, isopropyl-, butyl-, and isobutylparaben. Immature female rats were administered for 3 days from postnatal day 14 to 16 with 17α-ethinylestradiol (EE, 1 mg/kg body weight [BW]/day) or parabens (62.5, 250, and 1000 mg/kg BW/day). In uterotrophic assays, significantly increased uterus weights were detected in the EE-treated group and in the groups treated with the highest dose of isopropyl-, butyl-, and isobutylparaben. In addition, these parabens induced uterine CaBP-9k messenger RNA (mRNA) and protein levels, whereas cotreatment of parabens and fulvestrant, a pure estrogen receptor (ER) antagonist, completely reversed the paraben-induced gene expression and increased uterine weights. To investigate the ER-mediated mechanism(s) by which parabens exert their effects, the expression level of ER-α and progesterone receptor (PR) was analyzed. Exposure to EE or parabens caused a dramatic decrease in expression of both ER-α mRNA and protein levels, whereas cotreatment with fulvestrant reversed these effects. These data showed the difference of CaBP-9k and ER-α expression, suggesting that CaBP-9k may not express via ER-α pathway. In the effect of parabens on CaBP-9k expression through PR mediation, a significantly increased expression of uterine PR gene, a well-known ER-regulating gene, at both transcriptional and translational levels was indicated in the highest dose of isopropyl- and butylparaben. These parabens-induced PR gene expression was completely blocked by fulvestrant. This result indicates that CaBP-9k expression may involve with PR mediates in the estrogenic effect of paraben in immature rat uteri. Taken together, parabens exhibited an estrogen-like property in vivo, which may be mediated by a PR and/or ER-α signaling pathway. In addition, our results expanded the current understanding of the potential adverse effects of parabens associated with their estrogen-like activities. Further investigation is needed to elucidate in greater detail the adverse effects of parabens in humans and wildlife.

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An Evaluation of Estrogenic Activity of Parabens Using Uterine Calbindin-D9k Gene in an Immature Rat Model

Thuy T. B. Vo 0 Eui-Bae Jeung 0 0 Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University , Cheongju, Chungbuk 361-763 , Korea In the present study, calbindin-D9k (CaBP-9k), a potent biomarker for screening estrogen-like environmental chemicals in vivo and in vitro, was adopted to examine the potential estrogen-like property of the following parabens: propyl-, isopropyl-, butyl-, and isobutylparaben. Immature female rats were administered for 3 days from postnatal day 14 to 16 with 17aethinylestradiol (EE, 1 mg/kg body weight [BW]/day) or parabens (62.5, 250, and 1000 mg/kg BW/day). In uterotrophic assays, significantly increased uterus weights were detected in the EEtreated group and in the groups treated with the highest dose of isopropyl-, butyl-, and isobutylparaben. In addition, these parabens induced uterine CaBP-9k messenger RNA (mRNA) and protein levels, whereas cotreatment of parabens and fulvestrant, a pure estrogen receptor (ER) antagonist, completely reversed the paraben-induced gene expression and increased uterine weights. To investigate the ER-mediated mechanism(s) by which parabens exert their effects, the expression level of ER-a and progesterone receptor (PR) was analyzed. Exposure to EE or parabens caused a dramatic decrease in expression of both ER-a mRNA and protein levels, whereas cotreatment with fulvestrant reversed these effects. These data showed the difference of CaBP-9k and ER-a expression, suggesting that CaBP-9k may not express via ER-a pathway. In the effect of parabens on CaBP-9k expression through PR mediation, a significantly increased expression of uterine PR gene, a well-known ER-regulating gene, at both transcriptional and translational levels was indicated in the highest dose of isopropyl- and butylparaben. These parabensinduced PR gene expression was completely blocked by fulvestrant. This result indicates that CaBP-9k expression may involve with PR mediates in the estrogenic effect of paraben in immature rat uteri. Taken together, parabens exhibited an estrogen-like property in vivo, which may be mediated by a PR and/or ER-a signaling pathway. In addition, our results expanded the current understanding of the potential adverse effects of parabens associated with their estrogen-like activities. Further investigation is needed to elucidate in greater detail the adverse effects of parabens in humans and wildlife. - Recently, a variety of studies have focused on the hormonelike activities of environmental chemicals well known as xenobiotic estrogens in the environment, especially those related to the food industry or cosmetic products. It is reported that parabens possess a weak estrogenic activity (Ge and Chang, 2006; Lemini et al., 2003). These chemicals might cause disruption of endocrine systems and consequently influence the growth, differentiation, and function of reproductive systems. The potential adverse effects of parabens were reported for both in vivo and in vitro systems. In the rodents, a modification of uterine morphology and physiology was noted following treatment with parabens (Darbre et al., 2002, 2003; Routledge et al., 1998). Additionally, an alteration evoked by these chemicals in global patterns of gene expression caused aberrant estrogen signaling in cells and adversely influenced breast cancer development (Pugazhendhi et al., 2007; Terasaka et al., 2006). Parabens are quickly absorbed through the skin (Darbre et al., 2004) and are present in human breast tissue and milk (Donovan et al., 2004). The biological and toxicological effects of parabens on reproductive, cardiovascular, skeletal, and gastrointestinal system have also been demonstrated (Henry et al., 1993). Parabens are thought to be converted into p-hydroxybenzoic acid by hepatic metabolism, and this metabolite is detected in the blood and urine of mammals exposed to parabens (Soni et al., 2005). As parabens can mimic the effects of physiological estrogen, they bind to ERs, stimulate the ER-dependent response, and/or influence the expression of estrogen-responsive genes, including estrogen receptor alpha (ER-a), progesterone receptor (PR), and pS2 (Byford et al., 2002; Okubo et al., 2001). ERdependent estrogenic activities of parabens were demonstrated in MCF-7 human breast cancer cells (Byford et al., 2002; Okubo et al., 2001; Vanparys et al., 2006), ZR-75-1 cell lines (Darbre et al., 2004; Ge and Chang, 2006), rodent models (Darbre et al., 2003; Harvey, 2003; Kang et al., 2002; Oishi, 2002a,b), and fish (Inui et al., 2003). The estrogenic potency of parabens has been shown to depend on the lengths of their alkyl side chains (Darbre et al., 2003; Okubo et al., 2001). The estrogenicity of members of the paraben group, including methyl-, ethyl-, propyl-, butyl-, isobutyl-, isopropyl-, or benzylparabens, are distinct when compared to 17b-estradiol (E2), a natural estrogen (Byford et al., 2002; Lemini et al., 2003; Okubo e (...truncated)


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Thuy T. B. Vo, Eui-Bae Jeung. An Evaluation of Estrogenic Activity of Parabens Using Uterine Calbindin-D9k Gene in an Immature Rat Model, Toxicological Sciences, 2009, pp. 68-77, 112/1, DOI: 10.1093/toxsci/kfp176