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Hobler C, Andrade AJM, Grande SW, Gericke C, Talsness CE, Appel KE, Chahoud I, Grote K. Sex-dependent aromatase activity in rat offspring after pre- and postnatal exposure to triphenyltin chloride. Toxicology 2010; 276:198-205. [PMID: 20708649 DOI: 10.1016/j.tox.2010.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 08/03/2010] [Accepted: 08/05/2010] [Indexed: 11/19/2022]
Abstract
Triphenyltin (TPT) is an organotin compound (OTC) previously widely used as an antifouling agent in paints applied in the marine environment, a fungicide, and as an agricultural pesticide. In female aquatic invertebrates, certain OTCs induce the so-called imposex, an abnormal induction of male sex characteristics. OTC-induced environmental endocrine disruption also occurs in fish and mammals and a number of in vivo and in vitro studies have argued that OTCs may act through inhibition of the aromatase enzyme. In vivo studies supporting the aromatase inhibition hypothesis in mammals are lacking. Recently, the causal relationship between inhibition of aromatase and imposex was questioned, suggesting aromatase independent mechanisms of action for this phenomenon. We conducted a comprehensive investigation to identify the most sensitive window of exposure to TPTCl and to examine the effects of pre- and postnatal exposure on postnatal development in rats. The results on brain and gonadal aromatase activity obtained from offspring of dams exposed to 2 mg TPTCl/kg bw are reported here. Female and male offspring rats were exposed to 2 mg TPTCl/kg bw/d in utero from gestation day 6 through lactation until weaning on PND 21, or from gestation day 6 until termination at adulthood. Male offspring were sacrificed from PND 58 and female offspring at first estrus after PND 58. Pre- and postnatal TPT exposure clearly affected brain and gonadal aromatase activity in a sex-dependent fashion. While brain aromatase activity was significantly increased on PND 21 and at adulthood in female offspring, male offspring exhibited a significant decrease in brain aromatase activity only at adulthood. Ovarian aromatase activity was unaffected at both time points investigated. In contrast, testicular aromatase activity was significantly increased in males on PND 21 and significantly decreased at adulthood independent from the duration of treatment. The results of the present study confirm our previously reported observations regarding sex-dependent differences in sexual development after TPT exposure with the male rat being more susceptible to disturbances through this endocrine active compound than the female. We conclude that TPT administered during the particularly vulnerable period of development can affect aromatase activity in rats.
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Affiliation(s)
- Carolin Hobler
- Inst. of Clinical Pharmacology and Toxicology, Charité University Medical School, Campus Benjamin Franklin, 14195 Berlin, Germany
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102
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Rhind SM, Evans NP, Bellingham M, Sharpe RM, Cotinot C, Mandon-Pepin B, Loup B, Sinclair KD, Lea RG, Pocar P, Fischer B, van der Zalm E, Hart K, Schmidt JS, Amezaga MR, Fowler PA. Effects of environmental pollutants on the reproduction and welfare of ruminants. Animal 2010; 4:1227-1239. [PMID: 20582145 PMCID: PMC2888112 DOI: 10.1017/s1751731110000595] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 02/02/2010] [Indexed: 12/27/2022] Open
Abstract
Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.
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Affiliation(s)
- S. M. Rhind
- Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK
| | - N. P. Evans
- Division of Cell Sciences, Institute of Comparative Medicine, University of Glasgow Veterinary School, Glasgow G6 1QH, UK
| | - M. Bellingham
- Division of Cell Sciences, Institute of Comparative Medicine, University of Glasgow Veterinary School, Glasgow G6 1QH, UK
| | - R. M. Sharpe
- MRC Human Reproductive Sciences Unit, Queen’s Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - C. Cotinot
- INRA, UMR 1198, Biologie du Developpement et de la Reproduction 78350, Jouy-en-Josas, France
| | - B. Mandon-Pepin
- INRA, UMR 1198, Biologie du Developpement et de la Reproduction 78350, Jouy-en-Josas, France
| | - B. Loup
- INRA, UMR 1198, Biologie du Developpement et de la Reproduction 78350, Jouy-en-Josas, France
| | - K. D. Sinclair
- Schools of Biosciences, and Veterinary Medicine and Sciences, University of Nottingham, Leicestershire, LE12 5RD, UK
| | - R. G. Lea
- Schools of Biosciences, and Veterinary Medicine and Sciences, University of Nottingham, Leicestershire, LE12 5RD, UK
| | - P. Pocar
- Department of Animal Science, Division of Veterinary Anatomy and Histology, University of Milan, Via Celoria 10, 20133 Milano, Italy
| | - B. Fischer
- Department of Anatomy and Cell Biology, University of Halle, Grosse Steinstrasse 52, 06097 Halle, Germany
| | - E. van der Zalm
- Department of Anatomy and Cell Biology, University of Halle, Grosse Steinstrasse 52, 06097 Halle, Germany
| | - K. Hart
- Department of Anatomy and Cell Biology, University of Halle, Grosse Steinstrasse 52, 06097 Halle, Germany
| | - J.-S. Schmidt
- Department of Anatomy and Cell Biology, University of Halle, Grosse Steinstrasse 52, 06097 Halle, Germany
| | - M. R. Amezaga
- Centre for Reproductive Endocrinology & Medicine, Division of Applied Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - P. A. Fowler
- Centre for Reproductive Endocrinology & Medicine, Division of Applied Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
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103
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Ennulat D, Walker D, Clemo F, Magid-Slav M, Ledieu D, Graham M, Botts S, Boone L. Effects of Hepatic Drug-metabolizing Enzyme Induction on Clinical Pathology Parameters in Animals and Man. Toxicol Pathol 2010; 38:810-28. [DOI: 10.1177/0192623310374332] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hepatic drug-metabolizing enzyme (DME) induction is an adaptive response associated with changes in preclinical species; this response can include increases in liver weight, hepatocellular hyperplasia and hypertrophy, and upregulated tissue expression of DMEs. Effects of DME induction on clinical pathology markers of hepatobiliary injury and function in animals as well as humans are not well established. This component of a multipart review of the comparative pathology of xenobiotically mediated induction of hepatic metabolizing enzymes reviews pertinent data from retrospective and prospective preclinical and clinical studies. Particular attention is given to studies with confirmation of DME induction and concurrent evaluation of liver and/or serum hepatobiliary marker enzyme activities and histopathology. These results collectively indicate that in the rat, when histologic findings are limited to hepatocellular hypertrophy, DME induction is not expected to be associated with consistent or substantive changes in serum or plasma activity of hepatobiliary marker enzymes such as alanine aminotransferase, alkaline phosphatase, and gamma glutamyltransferase. In the dog and the monkey, published studies also do not demonstrate a consistent relationship across DME-inducing agents and changes in these clinical pathology parameters. However, increased liver alkaline phosphatase or gamma glutamyltransferase activity in dogs treated with phenobarbital or corticosteroids suggests that direct or indirect induction of select hepatobiliary injury markers can occur both in the absence of liver injury and independently of induction of DME activity. Although correlations between tissue and serum levels of these hepatobiliary markers are limited and inconsistent, increases in serum/plasma activities that are substantial or involve changes in other markers generally reflect hepatobiliary insult rather than DME induction. Extrahepatic effects, including disruption of the hypothalamic-pituitary-thyroid axis, can also occur as a direct outcome of hepatic DME induction in humans and animals. Importantly, hepatic DME induction and associated changes in preclinical species are not necessarily predictive of the occurrence, magnitude, or enzyme induction profile in humans.
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Affiliation(s)
| | - Dana Walker
- Bristol-Myers Squibb, East Syracuse, New York, USA
| | | | | | | | - Mark Graham
- AstraZeneca, Loughborough, Leicestershire, UK
| | | | - Laura Boone
- Covance Laboratories, Greenfield, Indiana, USA
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104
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le Maire A, Bourguet W, Balaguer P. A structural view of nuclear hormone receptor: endocrine disruptor interactions. Cell Mol Life Sci 2010; 67:1219-37. [PMID: 20063036 PMCID: PMC11115495 DOI: 10.1007/s00018-009-0249-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 12/03/2009] [Accepted: 12/22/2009] [Indexed: 01/14/2023]
Abstract
Endocrine-disrupting chemicals (EDCs) represent a broad class of exogenous substances that cause adverse effects in the endocrine system by interfering with hormone biosynthesis, metabolism, or action. The molecular mechanisms of EDCs involve different pathways including interactions with nuclear hormone receptors (NHRs) which are primary targets of a large variety of environmental contaminants. Here, based on the crystal structures currently available in the Protein Data Bank, we review recent studies showing the many ways in which EDCs interact with NHRs and impact their signaling pathways. Like the estrogenic chemical diethylstilbestrol, some EDCs mimic the natural hormones through conserved protein-ligand contacts, while others, such as organotins, employ radically different binding mechanisms. Such structure-based knowledge, in addition to providing a better understanding of EDC activities, can be used to predict the endocrine-disrupting potential of environmental pollutants and may have applications in drug discovery.
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Affiliation(s)
- Albane le Maire
- INSERM, U554, Centre de Biochimie Structurale, 34090 Montpellier, France
- CNRS, UMR5048, Universités Montpellier 1 & 2, 34090 Montpellier, France
| | - William Bourguet
- INSERM, U554, Centre de Biochimie Structurale, 34090 Montpellier, France
- CNRS, UMR5048, Universités Montpellier 1 & 2, 34090 Montpellier, France
| | - Patrick Balaguer
- Institut de Recherche en Cancérologie de Montpellier (IRCM), 34298 Montpellier, France
- INSERM, U896, 34298 Montpellier, France
- Université Montpellier 1, 34298 Montpellier, France
- CRLC Val d’Aurelle Paul Lamarque, 34298 Montpellier, France
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105
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Pavlikova N, Kortner TM, Arukwe A. Modulation of acute steroidogenesis, peroxisome proliferator-activated receptors and CYP3A/PXR in salmon interrenal tissues by tributyltin and the second messenger activator, forskolin. Chem Biol Interact 2010; 185:119-27. [PMID: 20211155 DOI: 10.1016/j.cbi.2010.03.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 02/24/2010] [Accepted: 03/01/2010] [Indexed: 10/19/2022]
Abstract
There are uncertainties regarding the role of sex steroids in sexual development and reproduction of gastropods, leading to the recent doubts as to whether organotin compounds do inhibit steroidogenic enzymes in these species. These doubts have led us to suspect that organotin compounds may affect other target molecules, particularly signal transduction molecules or secondary mediators of steroid hormone and lipid synthesis/metabolism. Therefore, we have studied the effects of TBT exposure through food on acute steroidogenesis, PPARs and CYP3A responses in the presence and absence of a cyclic AMP (cAMP) activator, forskolin. Two experiments were performed. Firstly, juvenile salmon were force-fed once with diet containing TBT doses (0.1, 1 and 10mg/kg fish) dissolved in ethanol and sampled after 72h. Secondly, fish exposed to solvent control and 10mg/kg TBT for 72h were transferred to new tanks and exposed to waterborne forskolin (200microg/L) for 2 and 4h. Our data show that juvenile salmon force-fed TBT showed modulations of multiple biological responses in interrenal tissues that include, steroidogenesis (cAMP/PKA activities; StAR and P450scc mRNA, and plasma cortisol), and mRNA for peroxisome proliferator-activated receptor (PPAR) isoforms (alpha, beta, gamma), acyl-CoA oxidase-1 (ACOX1) and CYP3A/PXR (pregnan X receptor). In addition, forskolin produced differential effects on these responses both singly and also in combination with TBT. Overall, combined forskolin and TBT exposure produced higher effects compared with TBT exposure alone, for most of the responses (cortisol, PPARbeta, ACOX1 and CYP3A). Interestingly, forskolin produced PPAR isoform-specific effects when given singly or in combination with TBT. Several TBT mediated toxicity in fish that includes thymus reduction, decrease in numbers of lymphocytes, inhibition of gonad development and masculinization, including the imposex phenomenon have been reported. When these effects are considered with the present findings, it suggests that studies on mechanisms of action or field studies may reveal endocrine, reproductive or other effects of TBT at lower concentrations than those reported to date from subchronic tests of fishes. Since the metabolic fate of organotin compounds may contribute to the toxicity of these chemicals, the present findings may represent some new aspects of TBT toxicity not previously reported.
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Affiliation(s)
- Nela Pavlikova
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
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106
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Abstract
Male infertility, characterized by hypogonadism, decreased semen quality or ejaculatory dysfunction, accounts for approximately 20% of infertility cases. Obesity and metabolic dysfunction have been identified, among other causal factors, to contribute to male infertility. In the context of the Western world's 'obesity epidemic', this article discusses three main biological mechanisms linking obesity to impaired male reproductive function: hypogonadism, testicular heat stress/hypoxia-induced apoptosis and endocrine disruption by 'obesogens'. Among these, obesity-induced hypogonadism is undoubtedly the most clinically significant and is easily assessed. Rapidly expanding areas of research in this area include leptin modulation of kisspeptins and hypothalamic-pituitary-testicular hormone pathways, and roles of other adipocytokines in male infertility, as well as the impact of exposure to obesogens on the quality of semen.
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Affiliation(s)
- Karen P Phillips
- a Assistant Professor, Interdisciplinary School of Health Sciences, Faculty of Health Sciences, Principal Scientist, Institute of Population Health, University of Ottawa, 43 Templeton Street, Room 215, Ottawa, ON K1N 6N5, Canada.
| | - Nongnuj Tanphaichitr
- b Senior Scientist, Ottawa Hospital Research Institute, and Professor in Obstetrics and Gynecology, and Biochemistry/Microbiology/Immunology, University of Ottawa, 725 Parkdale Avenue, Ottawa, ON K1Y 4E9, Canada.
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107
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Marsili L, Palmieri A, Petrini M. Reaction of carbon nucleophiles with alkylideneindazolium and alkylideneindolium ions generated from their 3-(1-arylsulfonylalkyl) indazole and indole precursors. Org Biomol Chem 2010; 8:706-12. [DOI: 10.1039/b919954c] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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108
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Sarpa M, Tavares Lopes CM, Delgado IF, Paumgartten FJR. Postnatal development and fertility of offspring from mice exposed to triphenyltin (fentin) hydroxide during pregnancy and lactation. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2010; 73:965-971. [PMID: 20563930 DOI: 10.1080/15287391003751752] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Fentin or triphenylthin (TPT) is an organotin compound (OTC) widely used as an agricultural fungicide and miticide. It is well known that TPT exerts adverse effects on the reproductive and immune systems and may disrupt the endocrine system, raising concerns regarding the risks posed by exposure to this metal on environmental and human health. In this study the effects of maternal exposure to TPT at doses of control (0), 1.875, 3.75, or 7.5 mg/kg body weight/d, po, were examined during gestation and lactation on offspring growth, organ weights, and fertility. Except for a significant liver enlargement at the highest dose, TPT produced no maternal toxicity. Increased neonatal mortality (death of 3 entire litters from a total of 18 treated litters) was noted at 7.5 mg/kg. Pup body weight at birth was significantly reduced at all dose levels, but no marked weight loss was found on postnatal day (PND) 5 and thereafter. Offspring maturation (ear unfolding, incisor eruption, vagina opening, and testes descent) and fertility in adulthood were not significantly affected by maternal exposure to TPT. In conclusion, data provided by this study indicate that maternal treatment with TPT during pregnancy and lactation delayed prenatal growth but did not impair postnatal development and fertility in exposed offspring in adulthood.
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Affiliation(s)
- Marcia Sarpa
- Laboratory of Environmental Toxicology, Department of Biological Sciences, National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
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109
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Sumpter JP. Protecting aquatic organisms from chemicals: the harsh realities. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:3877-3894. [PMID: 19736226 DOI: 10.1098/rsta.2009.0106] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Tens of thousands of man-made chemicals are in everyday use in developed countries. A high proportion of these, or their transformation products, probably reach the aquatic environment. A considerable amount is known about the environmental concentrations of some of these chemicals (such as metals), especially the regulated ones, but little or nothing is known about the majority. In densely populated countries, most or all rivers will receive both diffuse (e.g. agricultural runoff) and point source (e.g. sewage treatment plant effluent) inputs, and hence be contaminated with complex, ill-defined mixtures of chemicals. Most freshwater organisms will be exposed, to varying degrees, to this contamination. The number of species exposed is in the thousands, and quite possibly tens of thousands. Little is known about whether or not these species are adversely affected by the chemicals present in their environment. Often it is not even known what species are present, let alone whether they are affected by the chemicals present. In a few high-profile cases (e.g. tributyl tin causing imposex in molluscs and oestrogens 'feminizing' male fish), chemicals have undoubtedly adversely affected aquatic species, occasionally leading to population crashes. Whether or not other chemicals are affecting less visible species (such as most invertebrates) is largely unknown. It is possible that only very few chemicals in the freshwater environment are adversely affecting wildlife, but it is equally possible that some effects of chemicals are, as yet, undiscovered (and may remain so). Nor it is clear which chemicals may pose the greatest risk to aquatic organisms. All these uncertainties leave much to chance, yet designing a regulatory system that would better protect aquatic organisms from chemicals is difficult. A more flexible and intelligent strategy may improve the current situation. Finally, the risk due to chemicals is put into context with the many other threats, such as alien species and new diseases that undoubtedly can pose significant risks to aquatic ecosystems.
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Affiliation(s)
- John P Sumpter
- Institute for the Environment, Brunel University, , Uxbridge, Middlesex UB8 3PH, UK.
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110
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Hiromori Y, Nishikawa JI, Yoshida I, Nagase H, Nakanishi T. Structure-dependent activation of peroxisome proliferator-activated receptor (PPAR) gamma by organotin compounds. Chem Biol Interact 2009; 180:238-44. [PMID: 19497422 DOI: 10.1016/j.cbi.2009.03.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/06/2009] [Accepted: 03/10/2009] [Indexed: 11/28/2022]
Abstract
Organotin compounds such as tributyltin (TBT) and triphenyltin (TPT) are frequent environmental contaminants and are suspected of disrupting endocrine function in vertebrates and invertebrates. Previously, we reported that TBT and TPT function as powerful agonists for peroxisome proliferator-activated receptor (PPAR) gamma and stimulate adipocyte differentiation via the PPARgamma signaling pathway. Our current study investigates the structure-dependent binding of butyltin and phenyltin compounds to PPARgamma and their ability to activate the receptor. A Scatchard analysis with purified recombinant PPARgamma demonstrated that [(14)C]TPT binds to PPARgamma with an equilibrium dissociation constant (K(d)) of 66.6+/-5.2 nM, which approximated the 46.2+/-2.5 nM K(d) of a typical PPARgamma agonist, [(3)H]rosiglitazone (Rosi). TBT, TPT, diphenyltin (DPT), and tetrabutyltin (TeBT) blocked the binding of [(3)H]Rosi to PPARgamma in a competitive manner, and all tested organotin compounds except monobutyltin blocked the binding of [(14)C]TPT to PPARgamma in a competitive manner. Unexpectedly, Rosi did not compete at all with [(14)C]TPT for binding to PPARgamma, and contrary to the results of the competition assay, TBT and TeBT, but not dibutyltin, transcriptionally activated a GAL-PPARgamma chimeric receptor. All tested phenyltin compounds transcriptionally activated GAL-PPARgamma with an order of potency of TPT>DPT>monophenyltin. In addition, treatment of human choriocarcinoma cells with TBT, TeBT, and all tested phenyltin compounds stimulated production of human chorionic gonadotropin, which is upregulated by PPARgamma-mediated transcription. Our observations indicate that trialkylated and triphenylated tin compounds are the most potent PPARgamma agonists among the alkylated and phenylated tin compounds, and a phenyl substituent on a tin atom enhances the potency of organotin compounds as a PPARgamma agonist much more than a butyl substituent.
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Affiliation(s)
- Youhei Hiromori
- Laboratory of Hygienic Chemistry and Molecular Toxicology, Gifu Pharmaceutical University, Gifu, Japan
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111
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Activation of RXR-PPAR heterodimers by organotin environmental endocrine disruptors. EMBO Rep 2009; 10:367-73. [PMID: 19270714 DOI: 10.1038/embor.2009.8] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 01/15/2009] [Indexed: 11/09/2022] Open
Abstract
The nuclear receptor retinoid X receptor-alpha (RXR-alpha)-peroxisome proliferator-activated receptor-gamma (PPAR-gamma) heterodimer was recently reported to have a crucial function in mediating the deleterious effects of organotin compounds, which are ubiquitous environmental contaminants. However, because organotins are unrelated to known RXR-alpha and PPAR-gamma ligands, the mechanism by which these compounds bind to and activate the RXR-alpha-PPAR-gamma heterodimer at nanomolar concentrations has remained elusive. Here, we show that tributyltin (TBT) activates all three RXR-PPAR-alpha, -gamma, -delta heterodimers, primarily through its interaction with RXR. In addition, the 1.9 A resolution structure of the RXR-alpha ligand-binding domain in complex with TBT shows a covalent bond between the tin atom and residue Cys 432 of helix H11. This interaction largely accounts for the high binding affinity of TBT, which only partly occupies the RXR-alpha ligand-binding pocket. Our data allow an understanding of the binding and activation properties of the various organotins and suggest a mechanism by which these tin compounds could affect other nuclear receptor signalling pathways.
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112
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Alama A, Tasso B, Novelli F, Sparatore F. Organometallic compounds in oncology: implications of novel organotins as antitumor agents. Drug Discov Today 2009; 14:500-8. [PMID: 19429510 DOI: 10.1016/j.drudis.2009.02.002] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 01/30/2009] [Accepted: 02/03/2009] [Indexed: 01/11/2023]
Abstract
Since the introduction of cisplatin in cancer therapy, metal complexes and organometallic compounds have been gaining growing importance in oncology. The impressive clinical effectiveness of cisplatin is limited by significant side effects and the emergence of drug resistance. Thus, novel classic and unconventional Pt(II) and Pt(IV) complexes have been introduced in therapy or are presently in advanced clinical trials. Moreover, innovative non-platinum metal-based antitumor agents, whose activity does not rely on direct DNA damage and may involve proteins and enzymes, have been developed. Gold and tin derivatives are enjoying an increasing interest and appear very promising as potential drug candidates.
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Affiliation(s)
- Angela Alama
- Tumor Genetic, Lung Cancer Unit, National Institute for Cancer Research, Largo R. Benzi 10, 16132 Genoa, Italy.
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