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Do parabens have the ability to interfere with steroidogenesis?
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Abstracts / Toxicology Letters 180S (2008) S32–S246
MDM2. However, phosphorylation at serine 46 has been suggested to regulate p53-dependent apoptosis. Benzo(a)pyrene (BP), activated to BP-7,8-dihydrodiol-9,10-epoxide forming DNA adducts, induces apoptosis in mouse cell lines. We have studied the putative connection between BP-induced apoptosis and p53 phosphorylation at serine 46 in MCF-7 human breast carcinoma cells. Cell viability by MTT test and cell death by DNA content and PI exclusion test both analyzed by flow cytometry were studied after exposure to BP (1, 2.5 and 5 M). BP decreased viability of MCF-7 cells at 24, 48 and 72 h. Phosphorylation of p53 protein at serine 46 was seen already at 24 h after the addition of 2.5, 5, or 10 M BP. However, apoptosis as judged by the increase of subG1 fraction indicating fragmented DNA, was observed clearly only at 48 h and thereafter. Since phosphorylation of p53 at serine 46 increased earlier than DNA fragmentation, these results support p53 involvement in apoptosis of MCF-7 cells by BP. doi:10.1016/j.toxlet.2008.06.678 M34 Do parabens have the ability to interfere with steroidogenesis? Camilla Taxvig ∗ , Ulla Hass, Marta Axelstad, Julie Boberg, Pernille Reimer Hansen, Christine Nellemann National Food Institute, Technical University of Denmark, Department of Toxicology and Risk Assessment, DK-2860 Søborg, Denmark Parabens are used as preservatives in cosmetics, pharmaceuticals and in foods. They have been studied in a number of in vitro and in vivo systems. Many of the parabens have been shown to have weak estrogenic activity and some, including butylparaben, also caused reduction in testosterone levels and in sperm production in rats. However, more knowledge on the possible adverse effects of parabens on the endocrine system is needed. A combined in vitro/in vivo approach is a useful way to gain a complete understanding of the activities of the compound in question. In the current study, the effects of ethyl- and butylparaben on steroidogenesis were evaluated in rats exposed in utero. Additionally, both parabens were tested in vitro in the H295R steroidogenesis assay and in the T-screen assay. In the in utero exposure toxicity study, butylparaben caused a significant decrease in the mRNA expression level of ER-beta in foetal ovaries, and also significantly decreased the mRNA expression of StAR and Bzrp in the adrenal glands—both genes involved in an important step in steroidogenesis. In vitro butylparaben increased the proliferation of the GH3 cells in the T-Screen assay, thereby acting as a weak thyroid hormone receptor agonist. In the adrenal H295R steroidogenesis assay both ethyland butylparaben caused a significant increase in the progesterone formation. Overall, the results indicate that butylparaben might have the ability to act as an endocrine disruptor by interfering with the transport of cholesterol to the mitochondrion, thereby interfering with steroidogenesis Acknowledgement: This work is supported by the Danish Environmental protection agency (grant nos. 7041-0335, and 12310065). doi:10.1016/j.toxlet.2008.06.679
M35 The role of lipid peroxidation in the mechanism of organophosphates neurotoxicity Valerii Tonkopii Institute of Limnology, Rus. Acad. Sci., St. Petersburg, Russian Federation The acute toxicity of organophosphates (OPs) in mammals is primarily due to their irreversible inhibition of acetylcholinesterase in the nervous system which leads to increased synaptic acetylcholine levels. However, the toxic effect of some OPs is not limited to inhibition of cholinesterase: following the cholinergic crisis changes in non-cholinergic neurotoxic parameters, such as specific damage to cell membranes are observed. One of the major problems in assessing the role of lipid peroxidation in any chemical toxicity is to resolve whether this pathogenic cascade is a cause or a consequence of damage. The present study was undertaken to elucidate the relations between lipid peroxidation, OPs toxicity and delayed, long lasting, non-cholinergic changes. We studied the influence of OPs intoxication on lipid peroxidation in rat cerebral hemispheres. The level of lipid peroxidation was measured as the amount of common phospholipids, peroxidate lipids and malondialdehyde (MDA) in reaction with thiobarbituric acid. The rate of reaction of conditioned reflex of active avoidance was measured. Results were compared to those with pre-treatment with atropine and reversible cholinesterase inhibitor—galanthamine alone or together with different antioxidants (␣-tocopherol and oxymetacyl). OPs caused a rapid, dose-dependent increase of peroxidate lipids and MDA 15–30 days after intoxication. The level of lipid peroxidation correlated with the rate of conditioned reflex reaction. With paraoxon and sarin pre-treatment with atropine and galanthamine totally prevents the all symptoms of intoxication and changes in lipid peroxidation. Comparatively such type of prophylaxis in soman and malathion poisoned rats did not normalize the biochemical and physiological parameters. The protective effect of antioxidants against soman and malathion-induced lipid peroxidation was shown. Therefore, soman and malathion-associated lipid peroxidation is likely to arise mainly as a primary change which may, however, play a significant role in delayed neurotoxicity and conditioned reflex activity. doi:10.1016/j.toxlet.2008.06.680 M36 Effects of exposure to toluene on steroidogenesis in testes and aromatization of testosterone in brain of male rats during fetal life Shinji Tsukahara ∗ , Daisuke Nakajima, Yoshiko Kuroda, Rieko Hojo, Shiho Kageyama, Hidekazu Fujimaki National Institute for Environmental Studies, Tsukuba, Japan In developing rats, sexual differentiation of the brain involves effects of estradiol that is locally synthesized from testicular testosterone by aromatase in the brain. In the present study, we aimed to determine whether toluene affects steroidogenesis for testosterone and estradiol involved in the sexual differentiation of the brain. Pregnant rats were exposed to toluene at a dose of 0.9, 9, or 90 ppm for 90 min/day from gestational days (GDs) 15–19 via nasal inhalation. In male fetuses but not female fetuses on GD 19, the levels of plasma testosterone and brain estradiol determined by enzyme immunoassay were significantly reduced by toluene at 0.9, 9, and 90 ppm and at 9 and 90 ppm, respectively. In male fetuses on GD 19, we next examined effects of the toluene exposure on the mRNA levels of steroidogenic enzymes related in testosterone synthesis
Abstracts / Toxicology Letters 180S (2008) S32–S246
MDM2. However, phosphorylation at serine 46 has been suggested to regulate p53-dependent apoptosis. Benzo(a)pyrene (BP), activated to BP-7,8-dihydrodiol-9,10-epoxide forming DNA adducts, induces apoptosis in mouse cell lines. We have studied the putative connection between BP-induced apoptosis and p53 phosphorylation at serine 46 in MCF-7 human breast carcinoma cells. Cell viability by MTT test and cell death by DNA content and PI exclusion test both analyzed by flow cytometry were studied after exposure to BP (1, 2.5 and 5 M). BP decreased viability of MCF-7 cells at 24, 48 and 72 h. Phosphorylation of p53 protein at serine 46 was seen already at 24 h after the addition of 2.5, 5, or 10 M BP. However, apoptosis as judged by the increase of subG1 fraction indicating fragmented DNA, was observed clearly only at 48 h and thereafter. Since phosphorylation of p53 at serine 46 increased earlier than DNA fragmentation, these results support p53 involvement in apoptosis of MCF-7 cells by BP. doi:10.1016/j.toxlet.2008.06.678 M34 Do parabens have the ability to interfere with steroidogenesis? Camilla Taxvig ∗ , Ulla Hass, Marta Axelstad, Julie Boberg, Pernille Reimer Hansen, Christine Nellemann National Food Institute, Technical University of Denmark, Department of Toxicology and Risk Assessment, DK-2860 Søborg, Denmark Parabens are used as preservatives in cosmetics, pharmaceuticals and in foods. They have been studied in a number of in vitro and in vivo systems. Many of the parabens have been shown to have weak estrogenic activity and some, including butylparaben, also caused reduction in testosterone levels and in sperm production in rats. However, more knowledge on the possible adverse effects of parabens on the endocrine system is needed. A combined in vitro/in vivo approach is a useful way to gain a complete understanding of the activities of the compound in question. In the current study, the effects of ethyl- and butylparaben on steroidogenesis were evaluated in rats exposed in utero. Additionally, both parabens were tested in vitro in the H295R steroidogenesis assay and in the T-screen assay. In the in utero exposure toxicity study, butylparaben caused a significant decrease in the mRNA expression level of ER-beta in foetal ovaries, and also significantly decreased the mRNA expression of StAR and Bzrp in the adrenal glands—both genes involved in an important step in steroidogenesis. In vitro butylparaben increased the proliferation of the GH3 cells in the T-Screen assay, thereby acting as a weak thyroid hormone receptor agonist. In the adrenal H295R steroidogenesis assay both ethyland butylparaben caused a significant increase in the progesterone formation. Overall, the results indicate that butylparaben might have the ability to act as an endocrine disruptor by interfering with the transport of cholesterol to the mitochondrion, thereby interfering with steroidogenesis Acknowledgement: This work is supported by the Danish Environmental protection agency (grant nos. 7041-0335, and 12310065). doi:10.1016/j.toxlet.2008.06.679
M35 The role of lipid peroxidation in the mechanism of organophosphates neurotoxicity Valerii Tonkopii Institute of Limnology, Rus. Acad. Sci., St. Petersburg, Russian Federation The acute toxicity of organophosphates (OPs) in mammals is primarily due to their irreversible inhibition of acetylcholinesterase in the nervous system which leads to increased synaptic acetylcholine levels. However, the toxic effect of some OPs is not limited to inhibition of cholinesterase: following the cholinergic crisis changes in non-cholinergic neurotoxic parameters, such as specific damage to cell membranes are observed. One of the major problems in assessing the role of lipid peroxidation in any chemical toxicity is to resolve whether this pathogenic cascade is a cause or a consequence of damage. The present study was undertaken to elucidate the relations between lipid peroxidation, OPs toxicity and delayed, long lasting, non-cholinergic changes. We studied the influence of OPs intoxication on lipid peroxidation in rat cerebral hemispheres. The level of lipid peroxidation was measured as the amount of common phospholipids, peroxidate lipids and malondialdehyde (MDA) in reaction with thiobarbituric acid. The rate of reaction of conditioned reflex of active avoidance was measured. Results were compared to those with pre-treatment with atropine and reversible cholinesterase inhibitor—galanthamine alone or together with different antioxidants (␣-tocopherol and oxymetacyl). OPs caused a rapid, dose-dependent increase of peroxidate lipids and MDA 15–30 days after intoxication. The level of lipid peroxidation correlated with the rate of conditioned reflex reaction. With paraoxon and sarin pre-treatment with atropine and galanthamine totally prevents the all symptoms of intoxication and changes in lipid peroxidation. Comparatively such type of prophylaxis in soman and malathion poisoned rats did not normalize the biochemical and physiological parameters. The protective effect of antioxidants against soman and malathion-induced lipid peroxidation was shown. Therefore, soman and malathion-associated lipid peroxidation is likely to arise mainly as a primary change which may, however, play a significant role in delayed neurotoxicity and conditioned reflex activity. doi:10.1016/j.toxlet.2008.06.680 M36 Effects of exposure to toluene on steroidogenesis in testes and aromatization of testosterone in brain of male rats during fetal life Shinji Tsukahara ∗ , Daisuke Nakajima, Yoshiko Kuroda, Rieko Hojo, Shiho Kageyama, Hidekazu Fujimaki National Institute for Environmental Studies, Tsukuba, Japan In developing rats, sexual differentiation of the brain involves effects of estradiol that is locally synthesized from testicular testosterone by aromatase in the brain. In the present study, we aimed to determine whether toluene affects steroidogenesis for testosterone and estradiol involved in the sexual differentiation of the brain. Pregnant rats were exposed to toluene at a dose of 0.9, 9, or 90 ppm for 90 min/day from gestational days (GDs) 15–19 via nasal inhalation. In male fetuses but not female fetuses on GD 19, the levels of plasma testosterone and brain estradiol determined by enzyme immunoassay were significantly reduced by toluene at 0.9, 9, and 90 ppm and at 9 and 90 ppm, respectively. In male fetuses on GD 19, we next examined effects of the toluene exposure on the mRNA levels of steroidogenic enzymes related in testosterone synthesis