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Kim J, Konkel K, Diak IL, Glueck S, McCulley L. Letter to the Editor: Clinically Significant Hyperthyroidism and Hypothyroidism Following Exposure to Compounded Thyroid Products. Thyroid 2021; 31:143-146. [PMID: 32838690 PMCID: PMC7855378 DOI: 10.1089/thy.2020.0544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jenny Kim
- Division of Pharmacovigilance, Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Karen Konkel
- Division of Pharmacovigilance, Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Ida-Lina Diak
- Division of Pharmacovigilance, Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Shannon Glueck
- Division of Compounded Drugs, Office of Compliance, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Lynda McCulley
- Division of Pharmacovigilance, Office of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
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2
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Moffett SX, Klein EA, Brannigan G, Martin JV. L-3,3',5-triiodothyronine and pregnenolone sulfate inhibit Torpedo nicotinic acetylcholine receptors. PLoS One 2019; 14:e0223272. [PMID: 31584962 PMCID: PMC6777777 DOI: 10.1371/journal.pone.0223272] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 09/17/2019] [Indexed: 11/19/2022] Open
Abstract
The nicotinic acetylcholine receptor (nAChR) is an excitatory pentameric ligand-gated ion channel (pLGIC), homologous to the inhibitory γ-aminobutyric acid (GABA) type A receptor targeted by pharmaceuticals and endogenous sedatives. Activation of the GABAA receptor by the neurosteroid allopregnanolone can be inhibited competitively by thyroid hormone (L-3,3’,5-triiodothyronine, or T3), but modulation of nAChR by T3 or neurosteroids has not been investigated. Here we show that allopregnanolone inhibits the nAChR from Torpedo californica at micromolar concentrations, as do T3 and the anionic neurosteroid pregnenolone sulfate (PS). We test for the role of protein and ligand charge in mediated receptor inhibition by varying pH in a narrow range around physiological pH. We find that both T3 and PS become less potent with increasing pH, with remarkably similar trends in IC50 when T3 is neutral at pH < 7.3. After deprotonation of T3 (but no additional deprotonation of PS) at pH 7.3, T3 loses potency more slowly with increasing pH than PS. We interpret this result as indicating the negative charge is not required for inhibition but does increase activity. Finally, we show that both T3 and PS affect nAChR channel desensitization, which may implicate a binding site homologous to one that was recently indicated for accelerated desensitization of the GABAA receptor by PS.
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Affiliation(s)
- Steven X. Moffett
- Center for Computational and Integrative Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
| | - Eric A. Klein
- Center for Computational and Integrative Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
- Department of Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
- Department of Physics, Rutgers University—Camden, Camden, New Jersey, United States of America
| | - Joseph V. Martin
- Center for Computational and Integrative Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
- Department of Biology, Rutgers University—Camden, Camden, New Jersey, United States of America
- * E-mail:
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3
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Lazcano I, Hernández-Puga G, Robles JP, Orozco A. Alternative ligands for thyroid hormone receptors. Mol Cell Endocrinol 2019; 493:110448. [PMID: 31100496 DOI: 10.1016/j.mce.2019.05.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 05/08/2019] [Accepted: 05/13/2019] [Indexed: 12/21/2022]
Abstract
Thyroid hormone receptors (TRs) are ligand-dependent transcription factors that activate or repress gene transcription, resulting in the regulation of numerous physiological programs. While 3,3',5-L-triiodothyronine is the TR cognate ligand, these receptors can also be activated by various alternative ligands, including endogenous and synthetic molecules capable of inducing diverse active receptor conformations that influence thyroid hormone-dependent signaling pathways. This review mainly discusses current knowledge on 3,5-diiodo-L-thyronine and 3,5,3'-triiodothyroacetic acid, two endogenous molecules that bind to TRs and regulate gene expression; and the molecular interactions between TRs and ligands, like synthetic thyromimetics developed to target specific TR isoforms for tissue-specific regulation of thyroid-related disorders, or endocrine disruptors that have allowed the design of new analogues and revealed essential amino acids for thyroid hormone binding.
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Affiliation(s)
- Iván Lazcano
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Qro, Mexico; Departamento de Investigación Biomédica, Facultad de Medicina, Universidad Autónoma de Querétaro, Qro, Mexico
| | - Gabriela Hernández-Puga
- Departamento de Investigación Biomédica, Facultad de Medicina, Universidad Autónoma de Querétaro, Qro, Mexico
| | - Juan Pablo Robles
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Qro, Mexico
| | - Aurea Orozco
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Qro, Mexico.
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4
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Parizi MPS, Lastre Acosta AM, Ishiki HM, Rossi RC, Mafra RC, Teixeira ACSC. Environmental photochemical fate and UVC degradation of sodium levothyroxine in aqueous medium. Environ Sci Pollut Res Int 2019; 26:4393-4403. [PMID: 30109685 DOI: 10.1007/s11356-018-2907-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 08/03/2018] [Indexed: 06/08/2023]
Abstract
The synthetic hormone sodium levothyroxine (LTX) is one of the most prescribed drugs in the world and the most effective in hypothyroidism treatment. The presence of LTX in the environment has become a matter of major concern due to the widespread use of this hormone and by the fact that it is only partially removed in conventional water and sewage treatment plants. However, information regarding the photochemical fate of this hormone in environmental or engineered systems is scarce in the literature. In this work, the sunlight-driven direct and indirect LTX degradation was investigated by determining the photolysis quantum yield, ΦLTX = 3.80 (± 0.02) × 10-5, as well as the second-order kinetic constants of the reactions with hydroxyl radicals, kLTX,•OH = 1.50 (± 0.01) × 1010 L mol-1 s-1 and singlet oxygen, kLTX,1O2 = 1.47 (± 0.66) × 108 L mol-1 s-1. Mathematical simulations indicate that LTX photodegradation is favored in shallow, nitrite-rich, and dissolved organic matter (DOM)-poor environments, with LTX half-life times varying from less than 10 days to about 80 days. LTX removals of 85 and 95% were achieved by UVC photolysis and UVC/H2O2 after 120 min, respectively. Three transformation products, triiodothyronine, diiodothyronine, and diiodotyrosine, were identified during LTX degradation by the UVC-based processes studied. The results herein regarding photo-induced kinetics coupled with environmental fate simulations may help evaluate LTX persistence and also the design of water and wastewater treatment processes.
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Affiliation(s)
- Marcela Prado Silva Parizi
- Energy Engineering Department, São Paulo State University (UNESP), Barrageiros Av. 1881, Rosana, SP, Brazil.
| | - Arlen Mabel Lastre Acosta
- Research Group in Advanced Oxidation Processes, Chemical Systems Engineering Center, Department of Chemical Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, tr. 3, 380, São Paulo, SP, Brazil
| | - Hamilton Mitsugu Ishiki
- Environment and Regional Development, University of Western São Paulo (Unoeste), Presidente Prudente, SP, Brazil
| | - Renata Calciolari Rossi
- Environment and Regional Development, University of Western São Paulo (Unoeste), Presidente Prudente, SP, Brazil
| | - Renata Cristina Mafra
- Environment and Regional Development, University of Western São Paulo (Unoeste), Presidente Prudente, SP, Brazil
| | - Antonio Carlos Silva Costa Teixeira
- Research Group in Advanced Oxidation Processes, Chemical Systems Engineering Center, Department of Chemical Engineering, University of São Paulo, Av. Prof. Luciano Gualberto, tr. 3, 380, São Paulo, SP, Brazil
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5
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Stinckens E, Vergauwen L, Ankley GT, Blust R, Darras VM, Villeneuve DL, Witters H, Volz DC, Knapen D. An AOP-based alternative testing strategy to predict the impact of thyroid hormone disruption on swim bladder inflation in zebrafish. Aquat Toxicol 2018; 200:1-12. [PMID: 29702435 PMCID: PMC6002951 DOI: 10.1016/j.aquatox.2018.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 04/13/2018] [Accepted: 04/17/2018] [Indexed: 05/20/2023]
Abstract
The adverse outcome pathway (AOP) framework can be used to help support the development of alternative testing strategies aimed at predicting adverse outcomes caused by triggering specific toxicity pathways. In this paper, we present a case-study demonstrating the selection of alternative in chemico assays targeting the molecular initiating events of established AOPs, and evaluate use of the resulting data to predict higher level biological endpoints. Based on two AOPs linking inhibition of the deiodinase (DIO) enzymes to impaired posterior swim bladder inflation in fish, we used in chemico enzyme inhibition assays to measure the molecular initiating events for an array of 51 chemicals. Zebrafish embryos were then exposed to 14 compounds with different measured inhibition potentials. Effects on posterior swim bladder inflation, predicted based on the information captured by the AOPs, were evaluated. By linking the two datasets and setting thresholds, we were able to demonstrate that the in chemico dataset can be used to predict biological effects on posterior chamber inflation, with only two outliers out of the 14 tested compounds. Our results show how information organized using the AOP framework can be employed to develop or select alternative assays, and successfully forecast downstream key events along the AOP. In general, such in chemico assays could serve as a first-tier high-throughput system to screen and prioritize chemicals for subsequent acute and chronic fish testing, potentially reducing the need for long-term and costly toxicity tests requiring large numbers of animals.
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Affiliation(s)
- Evelyn Stinckens
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium; Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Gerald T Ankley
- United States Environmental Protection Agency, Mid-Continent Ecology Division,6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Ronny Blust
- Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Veerle M Darras
- Laboratory of Comparative Endocrinology, Department of Biology, KU Leuven, Naamsestraat 61, 3000 Leuven, Belgium
| | - Daniel L Villeneuve
- United States Environmental Protection Agency, Mid-Continent Ecology Division,6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Hilda Witters
- Applied Bio & Molecular Systems (ABS), Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium
| | - David C Volz
- Department of Environmental Sciences, University of California, 900 University Ave, Riverside, CA 92521, USA
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
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Kollitz EM, De Carbonnel L, Stapleton HM, Lee Ferguson P. The Affinity of Brominated Phenolic Compounds for Human and Zebrafish Thyroid Receptor β: Influence of Chemical Structure. Toxicol Sci 2018; 163:226-239. [PMID: 29409039 PMCID: PMC5920296 DOI: 10.1093/toxsci/kfy028] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Brominated phenolic compounds (BPCs) are found in the environment, and in human and wildlife tissues, and some are considered to have endocrine disrupting activities. The goal of this study was to determine how structural differences of 3 BPC classes impact binding affinities for the thyroid receptor beta (TRβ) in humans and zebrafish. BPC classes included halogenated bisphenol A derivatives, halogenated oxidative transformation products of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), and brominated phenols. Affinities were assessed using recombinant TRβ protein in competitive binding assays with 125I-triiodothyronine (125I-T3) as the radioligand. Zebrafish and human TRβ displayed similar binding affinities for T3 (Ki = 0.40 and 0.49 nM) and thyroxine (T4, Ki = 6.7 and 6.8 nM). TRβ affinity increased with increasing halogen mass and atomic radius for both species, with the iodinated compounds having the highest affinity within their compound classes. Increasing halogen mass and radius increases the molecular weight, volume, and hydrophobicity of a compound, which are all highly correlated with increasing affinity. TRβ affinity also increased with the degree of halogenation for both species. Human TRβ displayed higher binding affinities for the halogenate bisphenol A compounds, whereas zebrafish TRβ displayed higher affinities for 2,4,6-trichlorophenol and 2,4,6-trifluorophenol. Observed species differences may be related to amino acid differences within the ligand binding domains. Overall, structural variations impact TRβ affinities in a similar manner, supporting the use of zebrafish as a model for TRβ disruption. Further studies are necessary to investigate how the identified structural modifications impact downstream receptor activities and potential in vivo effects.
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Affiliation(s)
| | | | | | - Patrick Lee Ferguson
- Nicholas School of the Environment
- Pratt School of Engineering, Duke University, Durham, North Carolina 27708
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7
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Pireddu R, Pibiri M, Valenti D, Sinico C, Fadda AM, Simbula G, Lai F. A novel lactoferrin-modified stealth liposome for hepatoma-delivery of triiodothyronine. Int J Pharm 2018; 537:257-267. [PMID: 29294323 DOI: 10.1016/j.ijpharm.2017.12.048] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/29/2017] [Accepted: 12/30/2017] [Indexed: 01/10/2023]
Abstract
Triiodothyronine (T3), a thyroid hormone synthesized and secreted by the thyroid gland, plays an essential role in morphogenesis and differentiation through interaction with its nuclear receptors (TRs). However, there are increasing evidences for its role in hepatocellular carcinoma (HCC) suppression. The aim of this work was to develop an effective hepatocellular carcinoma targeting drug delivery system to improve T3 delivery to hepatic cancer cells as well as to reduce toxic side effects. Three different liposomal systems, such as unmodified, Stealth (PEGylated) and Lactoferrin (Lf)-modified-Stealth liposomes were successfully prepared by the film hydration method, and fully characterized. Liposome cell interactions and cellular uptake were evaluated in three different HCC target cells (FaO, HepG2 and SKHep) by confocal microscopy. Finally, in vitro cytotoxicity studies were carried out by using MTT assay to evaluate toxicity of the liposome delivery system and to test the effect of T3 when incorporated into liposomes. Internalization studies, performed using Lf-modified-liposomes labeled with the lipophilic marker Rho-PE and loaded with the hydrophilic probe CF, clearly demonstrated the effective internalization of both hydrophilic and lipophilic markers. Lf-liposomes might markedly enhance the specific cell binding and cellular uptake in hepatoma cells due to the mediating of Lf that could bind with high affinity to multiple receptors on cell surface, such as ASGP-R. Results obtained from this study highlight that the Lf- modified-liposomal delivery system may ensure a specific and sustained T3 delivery, thus, allowing reduced therapeutic doses and deleterious side effects of T3.
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Affiliation(s)
- Rosa Pireddu
- Università degli Studi di Cagliari, Dept. Scienze della Vita e dell'Ambiente, University of Cagliari, via Ospedale 72, 09124, Cagliari, Italy
| | - Monica Pibiri
- Università degli Studi di Cagliari, Dept. of Biomedical Sciences, University of Cagliari, via Porcell 4, Cagliari, 09124, Italy
| | - Donatella Valenti
- Università degli Studi di Cagliari, Dept. Scienze della Vita e dell'Ambiente, University of Cagliari, via Ospedale 72, 09124, Cagliari, Italy
| | - Chiara Sinico
- Università degli Studi di Cagliari, Dept. Scienze della Vita e dell'Ambiente, University of Cagliari, via Ospedale 72, 09124, Cagliari, Italy
| | - Anna Maria Fadda
- Università degli Studi di Cagliari, Dept. Scienze della Vita e dell'Ambiente, University of Cagliari, via Ospedale 72, 09124, Cagliari, Italy
| | - Gabriella Simbula
- Università degli Studi di Cagliari, Dept. of Biomedical Sciences, University of Cagliari, via Porcell 4, Cagliari, 09124, Italy
| | - Francesco Lai
- Università degli Studi di Cagliari, Dept. Scienze della Vita e dell'Ambiente, University of Cagliari, via Ospedale 72, 09124, Cagliari, Italy.
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8
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Richards K, Rijntjes E, Rathmann D, Köhrle J. Avoiding the pitfalls when quantifying thyroid hormones and their metabolites using mass spectrometric methods: The role of quality assurance. Mol Cell Endocrinol 2017; 458:44-56. [PMID: 28153800 DOI: 10.1016/j.mce.2017.01.032] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/20/2017] [Accepted: 01/20/2017] [Indexed: 01/05/2023]
Abstract
This short review aims to assess the application of basic quality assurance (QA) principles in published thyroid hormone bioanalytical methods using mass spectrometry (MS). The use of tandem MS, in particular linked to liquid chromatography has become an essential bioanalytical tool for the thyroid hormone research community. Although basic research laboratories do not usually work within the constraints of a quality management system and regulated environment, all of the reviewed publications, to a lesser or greater extent, document the application of QA principles to the MS methods described. After a brief description of the history of MS in thyroid hormone analysis, the article reviews the application of QA to published bioanalytical methods from the perspective of selectivity, accuracy, precision, recovery, instrument calibration, matrix effects, sensitivity and sample stability. During the last decade the emphasis has shifted from developing methods for the determination of L-thyroxine (T4) and 3,3',5-triiodo-L-thyronine (T3), present in blood serum/plasma in the 1-100 nM concentration range, to metabolites such as 3-iodo-L-thyronamine (3-T1AM), 3,5-diiodo-L-thyronine (3,5-T2) and 3,3'-diiodo-L-thyronine (3,3'-T2). These metabolites seem likely to be present in the low pM concentrations; consequently, QA parameters such as selectivity and sensitivity become more critical. The authors conclude that improvements, particularly in the areas of analyte selectivity, matrix effect measurement/documentation and analyte recovery would be beneficial.
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Affiliation(s)
- Keith Richards
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Eddy Rijntjes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Daniel Rathmann
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Josef Köhrle
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany.
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9
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Satish A, Korrapati PS. Tailored release of triiodothyronine and retinoic acid from a spatio-temporally fabricated nanofiber composite instigating neuronal differentiation. Nanoscale 2017; 9:14565-14580. [PMID: 28932862 DOI: 10.1039/c7nr05918c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Regeneration of the central and peripheral nervous system is challenging since the functional restoration of injured nerves is an incredible task. The fabrication of an ideal nerve guide that fulfills the requirement to regenerate nerve tissue is a herculean challenge requiring a combination of both biochemical and topographical cues. The present study explores the combinatorial effect of aligned nanofibers and the regulated delivery of triiodothyronine and retinoic acid on nerve regeneration. A sequential release mechanism is adopted in fabricating the nanofiber scaffold, with triiodothyronine incorporated into the nanofiber shell ensuring its prior release, followed by retinoic acid (entrapped within zein nanoparticles) from the core. The composite nanofibers thus fabricated possess excellent mechanical, physical and thermal properties and good topographical morphology and were highly biocompatible. The nanofibers were scrutinized for their efficacy in stimulating differentiation to a neuronal phenotype. The elongation factor (E-factor) of the neural cells had doubled in the bioactive incorporated composite compared to other scaffolds, as observed on phalloidin staining of their cytoskeleton, which endorsed enhanced neural differentiation on the fabricated nanofiber scaffold. There was a significant increase in the expression of neural-lineage specific markers on investigation of mRNA by real time PCR, showing a 10 fold increase in the gene expression of β-III-tubulin, a 5.5 fold increase for microtubule associated protein 2 gene and 3.5 fold for neurofilament M gene in the cells cultured over bioactive incorporated aligned nanofiber composites. Similarly protein expression was analyzed by immunofluorescence and flow cytometry studies, which showed an increase in the expression of β-III-tubulin in the composite nanofiber. This corroborates that neuronal differentiation is enhanced by the aligned nanotopography and spatio-temporal delivery of triiodothyronine and retinoic acid, opening avenues for nerve regenerative graft fabrication.
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Affiliation(s)
- Aishwarya Satish
- Biological Materials Laboratory, CSIR-Central Leather Research Institute, Chennai, India-600 020.
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10
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Bakhteyar H, Cassone C, Kohan HG, Sani SN. Kinetic Analysis of Drug Release from Compounded Slow-release Capsules of Liothyronine Sodium (T3). Int J Pharm Compd 2017; 21:418-425. [PMID: 29216618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The purpose of this study was to formulate extemporaneously compounded Liothyronine Sodium (T3) slow-release capsules and to evaluate their in vitro drug release performance. Twenty-one formulations containing T3 (7.5 µg) with various compositions of two different grades of Methocel E4M and K100M premium (30% to 90%), and/or SimpleCap/Lactose (10% to 70%) were examined. Quality assessment of the capsules was conducted by standard quality control criteria of the United States Pharmacopeia (i.e., weight variation, content uniformity) to ensure their compliance. The dissolution release profile of the formulations was evaluated using United States Pharmacopeia Apparatus type II (paddle method) at a speed of 50 rpm and temperature of 37°C in phosphate buffered saline media ( pH = 7.2 to 7.4). Aliquots from the media were taken periodically up to 24 hours and analyzed using a validated enzyme-linked immunosorbent assay method. The cumulative percentage of drug release for each formulation was fitted to eleven major release kinetic equations to determine the best-fit model of drug release, as well as the mechanism of release. Assay sensitivity was as low as 1 ng/mL and the optimal calibration range was found to be between 0 ng/mL and 7.5 ng/mL, which corresponded well with the average physiological plasma concentrations of T3. Liothyronine sodium with either SimpleCap (100%) or Methocel E4M (100%) exhibited slowrelease kinetic patterns of Peppas and Zero Order, respectively. The formulation with SimpleCap (100%) had a higher percentage of drug release (as compared to 100% Methocel E4M) within the first four hours; this formulation released 80% of the drug within 12 hours when the release was plateaued thereafter. The formulation with 30% Methocel E4M and 70% SimpleCap released 100% of the drug within the initial 12 hours and exhibited a Zero Order slow-release kinetic pattern. In general, the release kinetic rate of the formulations containing Methocel K100M appeared to be slower than Methocel E4M. This alteration may be due to a higher molecular weight and apparent viscosity of Methocel K100M. While most of the formulations were fitted to a slow-release kinetic pattern, several others including Methocel E4M 100%, 30% Methocel E4M+ 70% Simple Cap, 40% Methocel K100M+ 60% SimpleCap, 50% Methocel K100M+ 50% SimpleCap, 30% Methocel E4M+ 70% Lactose, 90% Methocel E4M+ 10% Lactose, 40% Methocel K100M+ 60% Lactose, and 50% Methocel K100M+ 50% Lactose followed an ideal slow-release kinetic pattern of Zero Order or Higuchi. The results of this study successfully demonstrated the optiomal composition of slow-release compounded capsules of T3. Future studies are warranted to evaluate the in vivo performance of the optimal formulations and to establish an in vitro-in vivo correlation.
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Affiliation(s)
- Hamid Bakhteyar
- Carolina Compounding Pharmacy & Health Center, Cary, North Carolina
| | - Clayton Cassone
- Western New England University, College of Pharmacy, Department of Pharmaceutical & Administrative Sciences, Springfield, Massachusetts
| | - Hamed Gilzad Kohan
- Western New England University, College of Pharmacy, Department of Pharmaceutical & Administrative Sciences, Springfield, Massachusetts
| | - Shabnam N Sani
- Western New England University, College of Pharmacy, Department of Pharmaceutical & Administrative Sciences, Springfield, Massachusetts.
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11
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Seger CD, He X, Braverman LE, Yeh MW, Bernet VJ, Singh RJ, Rhee CM, Leung AM. Negligible Thyroid Hormone Content Present in Nonprescription U.S. Weight Loss Products. Thyroid 2017; 27:300-301. [PMID: 27897088 PMCID: PMC5314722 DOI: 10.1089/thy.2016.0534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Xuemei He
- Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, Massachusetts
| | - Lewis E. Braverman
- Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, Massachusetts
| | - Michael W. Yeh
- UCLA David Geffen School of Medicine, Los Angeles, California
- Section of Endocrine Surgery, UCLA David Geffen School of Medicine, Los Angeles, California
| | - Victor J. Bernet
- Division of Endocrinology, Mayo Clinic Florida, Jacksonville, Florida
| | - Ravinder J. Singh
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Connie M. Rhee
- Division of Nephrology and Hypertension, University of California Irvine, Irvine, California
| | - Angela M. Leung
- Division of Endocrinology, UCLA David Geffen School of Medicine, Los Angeles, California
- Division of Endocrinology, VA Greater Los Angeles Healthcare System, Los Angeles, California
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12
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Duntas LH, Wartofsky L. There is no 'universal fit': Reflections on the use of l-triiodothyronine in the treatment of hypothyroidism. Metabolism 2016; 65:428-31. [PMID: 26975534 DOI: 10.1016/j.metabol.2015.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 11/08/2015] [Accepted: 11/12/2015] [Indexed: 11/28/2022]
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Olvera A, Mendoza A, Villalobos P, Mayorga-Martínez L, Orozco A, Valverde-R C. The variable region of iodothyronine deiodinases directs their catalytic properties and subcellular localization. Mol Cell Endocrinol 2015; 402:107-12. [PMID: 25591907 DOI: 10.1016/j.mce.2015.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/08/2015] [Accepted: 01/08/2015] [Indexed: 11/19/2022]
Abstract
The stereospecific removal of iodine from thyroid hormones is an essential first step for T3 action and is catalyzed by three different deiodinases: D2 and D3 remove iodine only from the outer or inner ring, respectively, whereas D1 catalyzes both pathways. We used in silico predictions from vertebrate deiodinase sequences to identify two domains: the N-terminal variable region (VR) containing the transmembrane, hinge and linker domains, and the conserved or globular region (CR). Given the high sequence and structural identity of the CR among paralogs as well as of the VR among orthologs but not paralogs, we hypothesized that both the catalytic properties and the subcellular localization rely on the VR. We used shark D2 and D3 as templates to build the chimeric enzymes D2VR/D3CR and D3VR/D2CR. Biochemical characterization revealed that D3VR/D2CR has inner-ring deiodination activity and T3 as preferred substrate, whereas D2VR/D3CR showed no deiodinating activity. Also, D2VR/D3CR and D3VR/D2CR reside in the endoplasmic reticulum and plasmatic membrane, respectively, as do their D2 and D3 wild-type counterparts. We conclude that the VR determines the subcellular localization and is critical in defining the catalytic properties and activity of thyroid hormone deiodinases.
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Affiliation(s)
- Aurora Olvera
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
| | - Arturo Mendoza
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
| | - Patricia Villalobos
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
| | - Lidia Mayorga-Martínez
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
| | - Aurea Orozco
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
| | - Carlos Valverde-R
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
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Oda T, Taneichi H, Takahashi K, Togashi H, Hangai M, Nakagawa R, Ono M, Matsui M, Sasai T, Nagasawa K, Honma H, Kajiwara T, Takahashi Y, Takebe N, Ishigaki Y, Satoh J. Positive association of free triiodothyronine with pancreatic β-cell function in people with prediabetes. Diabet Med 2015; 32:213-9. [PMID: 25255697 DOI: 10.1111/dme.12589] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/19/2014] [Indexed: 12/12/2022]
Abstract
AIM To analyse the effects of thyroid hormones on β-cell function and glucose metabolism in people with prediabetes who are euthyroid. METHODS A total of 111 people who were euthyroid underwent 75-g oral glucose tolerance tests, of whom 52 were assigned to the normal glucose tolerance and 59 to the prediabetes groups. Homeostatic model assessment of β-cell function, insulinogenic index and areas under the curve for insulin and glucose were evaluated as indices of pancreatic β-cell function. RESULTS In both groups, BMI, fasting insulin, homeostasis model assessment ratio and HDL cholesterol correlated significantly with all indices of pancreatic β-cell function. Free triiodothyronine correlated positively with all insulin secretion indices in the prediabetes group. Multiple linear regression analysis showed that free triiodothyronine was an independent variable that had a positive correlation with all indices of β-cell function in the prediabetes group. By contrast, no such correlation was found in the normal glucose tolerance group. CONCLUSIONS Free triiodothyronine is associated with both basal and glucose-stimulated insulin secretion in people with prediabetes who are euthyroid; therefore, the regulation of insulin secretion by thyroid hormones is a potentially novel therapeutic target for the treatment of diabetes.
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Affiliation(s)
- T Oda
- Division of Diabetes and Metabolism, Department of Internal Medicine, Iwate Medical University, Morioka, Japan
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15
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Zhang Q, Lian XL, Chai XF, Bai Y, Dai WX. [Relationship between maternal milk and serum thyroid hormones in patients with thyroid related diseases]. Zhongguo Yi Xue Ke Xue Yuan Xue Bao 2013; 35:427-431. [PMID: 23987491 DOI: 10.3881/j.issn.1000-503x.2013.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
OBJECTIVE To explore the relationship between maternal milk and serum thyroid hormones in patients with thyroid-related diseases. METHODS Serum and breast milk samples were collected from 56 breastfeeding mothers. Milk and serum free triiodothyronine (FT3), free thyroxine (FT4), triiodothyronine(T3), thyroxine (T4), and thyrotrophin (TSH) were determined, and T3/T4 was calculated. Using the serum thyroid hormones as the independent variables and milk thyroid hormones as the dependent variables, we performed linear regression analysis. RESULTS The milk FT3, FT4, T3, T4, TSH, and T3/T4 were (2.30 ± 0.82) pg/ml ,(0.45 ± 0.26) ng/dl, (0.35 ± 0.20) ng/ml, (2.96 ± 1.55) Μg/dl, (0.12 ± 0.08) ΜU/ml, and 0.12 ± 0.04, respectively. Milk FT3 (r = 0.778, P = 0.000), T3 (r = 0.603, P = 0.000), T4 (r = 0.485, P = 0.004), and TSH (r = 0.605, P = 0.000) concentrations were positively correlated with those in serum. CONCLUSION Thyroid hormones are present in human milk and are positively correlated with those in serum.
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Affiliation(s)
- Qian Zhang
- Department of Endocrinology, PUMC Hospital, Beijing, China
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16
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Tóth G, Noszál B. [Thyroid hormones and their precursors I. Biochemical properties]. Acta Pharm Hung 2013; 83:35-45. [PMID: 23926648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This paper and the following one (see the next issue of Acta Pharmaceutica Hungarica) survey the biological roles and the related site-specific physico-chemical parameters (basicity and lipophilicity) of the presently known thyroid hormones (thyroxine, liothyronine and reverse liothyronine) and their biological precursors (monoiodotyrosine and diiodotyrosine). Here the literature of the thyroid hormone biochemistry, biosynthesis, plasma- and membrane transport is summarized, focusing on the pH-dependent processes. Biosyntheses of the thyroid hormones take place by oxidative coupling of two iodotyrosine residues catalyzed by thyreoperoxidase in thyreoglobulin. The protonation state of the precursors, especially that of the phenolic OH is crucial for the biosynthesis, since anionic iodotyrosine residues can only be coupled in the thyroid hormone biosyntheses. In the blood more than 99% of the circulating thyroid hormone is bound to plasma proteins among which the thyroxine-binding globulin and transthyretin are crucial. The amphiphilic character of the hormones is assumed to be the reason why their membrane transport is an energy-dependent, transport-mediated process, in which the organic anion transporter family, mainly OATP1C1, and the amino acid transporters, such as MCT8 play important roles. Liothyronine is the biologically active hormone; it binds the thyroid hormone receptor, a type of nuclear receptor. There are two major thyroid hormone receptor (TR) isoforms, alfa (TRalpha) and beta (TRbeta). The activation of the TRalpha is associated with modifications in cardiac behavior, while activation of the TRbeta is associated with increasing metabolic rates, resulting in weight loss and reduction of blood plasma lipid levels. The affinity of the thyroid hormones for different proteins depends on the ionization state of the ligands. The site-specific physico-chemical characterization of the thyroid hormones is of fundamental importance to understand their (patho)physiological behavior and also, to influence their therapeutic properties at the molecular level.
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Affiliation(s)
- Gergo Tóth
- Semmelweis Egyetem, Gyógyszerészi Kémiai Intézet, Magyar Tudományos Akadémia Kábító- és Doppingszer-tudomdányi Társult Kutatócsoport, Budapest, Hogyes Endre utca 9.
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Abstract
There is significant interest in development of thyroid hormone analogues to harness specific properties as therapeutic agents for a variety of clinical indications including obesity, hypercholesterolemia, heart failure, and thyrotoxicosis. To date, most analogues have been designed to target liver specific effects, which can promote weight loss and lipid lowering through either tissue specific uptake or thyroid hormone receptor (TR) β isoform selectivity at the same time minimizing the unwanted cardiac and bone effects. We have developed a molecular biomarker assay to study the induction of the transcription of the cardiac specific α-myosin heavy chain (MHC) gene as a more sensitive and specific measure of thyroid hormone action on cardiac myocytes. We tested 5 TRβ and 1 TRα selective agonists as well as 2 putative TR antagonists in our α-MHC hnRNA assay. Using reverse transcription and polymerase chain reaction, we measured the induction of the α-MHC primary transcript in response to administration of drug. The TRα and only 2 of the TRβ agonists were highly active, when compared to the effect of T3, at the level of the cardiac myocyte. In addition, our data suggests that the reason that the antagonist NH-3 is not able to block the T3-mediated induction of α-MHC is that it does not get transported into the cardiac myocyte. Our data suggest that this assay will be useful in preclinical studies of the potential cardiac specific effects of thyroid hormone analogues and that predictions of function based on structure are not necessarily accurate or complete.
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Affiliation(s)
- S Danzi
- Department of Medicine, North Shore University Hospital and Feinstein Institute for Medical Research, Manhasset, New York, USA.
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18
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Abstract
T4 is a prohormone secreted by the thyroid. T4 has a long half life in circulation and it is tightly regulated to remain constant in a variety of circumstances. However, the availability of iodothyronine selenodeiodinases allow both the initiation or the cessation of thyroid hormone action and can result in surprisingly acute changes in the intracellular concentration of the active hormone T3, in a tissue- specific and chronologically-determined fashion, in spite of the constant circulating levels of the prohormone. This fine-tuning of thyroid hormone signaling is becoming widely appreciated in the context of situations where the rapid modifications in intracellular T3 concentrations are necessary for developmental changes or tissue repair. Given the increasing availability of genetic models of deiodinase deficiency, new insights into the role of these important enzymes are being recognized. In this review, we have incorporated new information regarding the special role played by these enzymes into our current knowledge of thyroid physiology, emphasizing the clinical significance of these new insights.
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Affiliation(s)
- Alessandro Marsili
- Thyroid Section, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Ann Marie Zavacki
- Thyroid Section, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - John W. Harney
- Thyroid Section, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - P. Reed Larsen
- Thyroid Section, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Kumar AP, Jin H, Jo SC, Kim C, Nam SH, Lee YI. Isomeric discrimination and quantification of thyroid hormones, T3 and rT3, by the single ratio kinetic method using electrospray ionization mass spectrometry. J Am Soc Mass Spectrom 2010; 21:14-22. [PMID: 19853471 DOI: 10.1016/j.jasms.2009.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 07/02/2009] [Accepted: 07/02/2009] [Indexed: 05/28/2023]
Abstract
The single ratio kinetic method is applied to the discrimination and quantification of the thyroid hormone isomers, 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine, in the gas phase, based on the kinetics of the competitive unimolecular dissociations of singly charged transition-metal ion-bound trimeric complexes [M(II)(A)(ref*)(2)-H](+) (M(II) = divalent transition-metal ion; A = T(3) or rT(3); ref* = reference ligand). The trimeric complex ions are generated using electrospray ionization mass spectrometry and the ions undergo collisional activation to realize isomeric discrimination from the branching ratio of the two fragment pathways that form the dimeric complexes [M(II)(A)(ref*)-H](+) and [M(II)(ref*)(2)-H](+). The ratio of the individual branching ratios for the two isomers R(iso) is found strongly dependent on the references and the metal ions. Various sets are tried by choosing the reference from amino acids, substituted amino acids, and dipeptides in combination with the central metal ion chosen from five transition-metal ions (Co(II), Cu(II), Mn(II), Ni(II), and Zn(II)) for the complexes in this experiment. The results are compared in terms of the isomeric discrimination for the T(3)/rT(3) pair. Calibration curves are constructed by relating the ratio of the branching ratios against the isomeric composition of their mixture to allow rapid quantitative isomer analysis of the sample pair. Furthermore, the instrument-dependence of this method is investigated by comparing the two sets of results, one obtained from a quadrupole ion trap mass spectrometer and the other from a quadrupole time-of-flight mass spectrometer.
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20
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Rudolph C, Sieverling N, Schillinger U, Lesina E, Plank C, Thünemann AF, Schönberger H, Rosenecker J. Thyroid hormone (T3)-modification of polyethyleneglycol (PEG)-polyethyleneimine (PEI) graft copolymers for improved gene delivery to hepatocytes. Biomaterials 2007; 28:1900-11. [PMID: 17196251 DOI: 10.1016/j.biomaterials.2006.12.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 12/04/2006] [Indexed: 10/23/2022]
Abstract
Targeting of gene vectors to liver hepatocytes could offer the opportunity to cure various acquired and inherited diseases. Efficient gene delivery to the liver parenchyma has been obscured from efficient targeting of hepatocytes. Here we show that the thyroid hormone, triiodothyronine (T3), can be used to improve the gene transfer efficiency of nonviral gene vectors to hepatocytes in vitro and to the liver of mice in vivo. T3 conjugated to the distal ends of fluorescent labeled PEG-g-dextran resulted in T3-specific cellular endosomal uptake into the hepatocellular cell line HepG2. PEG-g-PEI graft copolymers with increasing molar PEG-ratios were synthesized, complexed with plasmid DNA, and transfected into HepG2 or HeLa cells. Gene transfer efficiency decreased as the number of PEG blocks increased. T3 conjugation to PEI and the distal ends of PEG blocks resulted in T3 specific gene transfer in HepG2 cells as evidenced by reduction of gene transfer efficiency after pre-incubation of cells with excess of T3. In vivo application of T3-PEG-g-PEI based gene vectors in mice after tail vein injection resulted in a significantly 7-fold increase of gene expression in the liver compared with PEG-g-PEI based gene vectors.
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Affiliation(s)
- Carsten Rudolph
- Department of Pediatrics, Ludwig-Maximilians University, 80337 Munich, Germany.
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21
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Figueira ACM, Neto MDO, Bernardes A, Dias SMG, Craievich AF, Baxter JD, Webb P, Polikarpov I. Low-resolution structures of thyroid hormone receptor dimers and tetramers in solution. Biochemistry 2007; 46:1273-83. [PMID: 17260956 DOI: 10.1021/bi061698h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-resolution X-ray structures of thyroid hormone (TH) receptor (TR) DNA and ligand binding domains (DBD and LBD) have yielded significant insights into TR action. Nevertheless, the TR DBD and LBD act in concert to mediate TH effects upon gene expression, and TRs form multiple oligomers; however, structures of full-length TRs or DBD-LBD constructs that would clarify these influences are not available. Here, we report low-resolution X-ray structures of the TRbeta DBD-LBD construct in solution which define the shape of dimers and tetramers and likely positions of the DBDs and LBDs. The holo TRbeta DBD-LBD construct forms a homodimer with LBD-DBD pairs in close contact and DBDs protruding from the base in the same direction. The DBDs are connected to the LBDs by crossed extended D domains. The apo hTRbeta DBD-LBD construct forms tetramers that resemble bulged cylinders with pairs of LBD dimers in a head-to-head arrangement with DBD pairs packed tightly against the LBD core. Overall, there are similarities with our previous low-resolution structures of retinoid X receptors, but TRs exhibit two unique features. First, TR DBDs are closely juxtaposed in the dimer and tetramer forms. Second, TR DBDs are closely packed against LBDs in the tetramer, but not the dimer. These findings suggest that TRs may be able to engage in hitherto unknown interdomain interactions and that the D domain must rearrange in different oligomeric forms. Finally, the data corroborate our suggestion that apo TRs form tetramers in solution which dissociate into dimers upon hormone binding.
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Affiliation(s)
- Ana Carolina Migliorini Figueira
- Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador Sãocarlense, 400, São Carlos, SP, Brazil 13560-970
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22
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Veldhoen N, Skirrow RC, Osachoff H, Wigmore H, Clapson DJ, Gunderson MP, Van Aggelen G, Helbing CC. The bactericidal agent triclosan modulates thyroid hormone-associated gene expression and disrupts postembryonic anuran development. Aquat Toxicol 2006; 80:217-27. [PMID: 17011055 DOI: 10.1016/j.aquatox.2006.08.010] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 08/17/2006] [Accepted: 08/30/2006] [Indexed: 05/12/2023]
Abstract
We investigated whether exposure to environmentally relevant concentrations of the bactericidal agent, triclosan, induces changes in the thyroid hormone-mediated process of metamorphosis of the North American bullfrog, Rana catesbeiana and alters the expression profile of thyroid hormone receptor (TR) alpha and beta, basic transcription element binding protein (BTEB) and proliferating nuclear cell antigen (PCNA) gene transcripts. Premetamorphic tadpoles were immersed in environmentally relevant concentrations of triclosan and injected with 1 x 10(-11)mol/g body weight 3,5,3'-triiodothyronine (T3) or vehicle control. Morphometric measurements and steady-state mRNA levels obtained by quantitative polymerase chain reaction were determined. mRNA abundance was also examined in Xenopus laevis XTC-2 cells treated with triclosan and/or 10nM T3. Tadpoles pretreated with triclosan concentrations as low as 0.15+/-0.03 microg/L for 4 days showed increased hindlimb development and a decrease in total body weight following T3 administration. Triclosan exposure also resulted in decreased T3-mediated TRbeta mRNA expression in the tadpole tail fin and increased levels of PCNA transcript in the brain within 48 h of T3 treatment whereas TRalpha was unaffected [corrected] Triclosan alone altered thyroid hormone receptor alpha transcript levels in the brain of premetamorphic tadpoles and induced a transient weight loss. In XTC-2 cells, exposure to T3 plus nominal concentrations of triclosan as low as 0.03 microg/L for 24h resulted in altered thyroid hormone receptor mRNA expression. Exposure to low levels of triclosan disrupts thyroid hormone-associated gene expression and can alter the rate of thyroid hormone-mediated postembryonic anuran development.
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Affiliation(s)
- Nik Veldhoen
- Department of Biochemistry and Microbiology, P.O. Box 3055, Stn. CSC, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
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Koidl J, Hödl H, Schmid MG, Konrad M, Petschauer S, Kostner GM, Gübitz G. Chiral separation of T3 enantiomers using stereoselective antibodies as a selector in micro-HPLC. J Biochem Biophys Methods 2006; 69:33-42. [PMID: 16697467 DOI: 10.1016/j.jbbm.2006.03.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Revised: 03/21/2006] [Accepted: 03/26/2006] [Indexed: 11/19/2022]
Abstract
This work deals with the application of stereoselective antibodies against L-T3 as a tailor-made chiral selector in micro-HPLC. The separations were performed in microbore columns using commercially available anti-L-T3 antibodies chemically bonded to 5 microm silica gel. The enantiomers of T3 were baseline separated under mild continuous isocratic elution conditions using 10 mM phosphate buffer, pH 7.4. The D-enantiomer eluted with the void volume, while the L-enantiomer was retained by the antibody phase and eluted second. An indirect competitive and non-competitive enzyme linked immunosorbent assay (ELISA) was used for testing the stereoselectivity of anti-L-T3 antibodies.
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Affiliation(s)
- Julia Koidl
- Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, Karl-Franzens-University, Universitätsplatz 1, A-8010 Graz, Austria
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Cai Y, Meng XF, Cao YX, Lu H, Zhu SF, Zhou LZ. Montmorillonite ameliorates hyperthyroidism of rats and mice attributed to its adsorptive effect. Eur J Pharmacol 2006; 551:156-61. [PMID: 17027745 DOI: 10.1016/j.ejphar.2006.08.053] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 08/19/2006] [Accepted: 08/23/2006] [Indexed: 11/25/2022]
Abstract
The present study aims to evaluate the adsorbing effect of montmorillonite on thyroid hormone in the entero-hepatic circulation. The concentration of thyroid hormone in the serum of hyperthyroidism model rats and in solution was measured by radioimmunoassay and ultraviolet spectrometry, respectively. The body weight, temperature, and consumption of food and water were observed in hyperthyroidism model rats. Furthermore, hypoxia tolerance, sodium-pentobarbital-induced sleep time, spontaneous activities were measured on hyperthyroidism model mice after being treated with montmorillonite. Results showed that montmorillonite adsorbed thyroxin (T(4)) and triiodothyronine (T(3)) in vitro. Montmorillonite at dosage of 1.0 g/kg and 0.3 g/kg decreased thyroid hormone levels on hyperthyroidism model rats; Montmorillonite (2.0 g/kg and 0.6 g/kg) prolonged the sleep time, improved the hypoxia tolerant capacity and reduced the spontaneous activities of the hyperthyroidism model mice. These results suggest montmorillonite has anti-hyperthyroidism effect attributed to its adsorptive effect.
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Affiliation(s)
- Yan Cai
- Department of Pharmacology, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi, 710061, PR China
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Hassan AQ, Koh JT. A functionally orthogonal ligand-receptor pair created by targeting the allosteric mechanism of the thyroid hormone receptor. J Am Chem Soc 2006; 128:8868-74. [PMID: 16819881 PMCID: PMC2515387 DOI: 10.1021/ja060760v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Nuclear receptors are ligand-dependent transcription factors that are of interest as potential tools to artificially regulate gene expression. Ligand binding induces a conformational change involving helix-12 which forms part of the dimerization interface used to bind transcriptional coactivators. When triiodothyronine (T3) binds the thyroid hormone receptor (TR) it indirectly contacts helix-12 through intermediary residues His(435) and Phe(451) termed a His-Phe switch. The mutant TRbeta(H435A) is nonresponsive to physiological concentrations of T3 but can be activated by the synthetic hormone analogue QH2 which potently activates His435-->Ala mutant at concentrations that do not activate the wild-type receptors TRalpha and TRbeta. QH2 does not show antagonist behavior with the wild-type TRs. QH2's functionally orthogonal behavior with TRbeta(H435A) is preserved on the three consensus thyroid hormone response elements.
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Affiliation(s)
- A. Quamrul Hassan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - John T. Koh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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26
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Abstract
Recent identification of membrane receptors for T4, T3, 3,5-T2, and 3-iodothyronamine that mediate rapid physiologic effects of thyroid hormones suggested that such receptors may supplement the regulation of TRH and TRH-like peptides by nuclear T3 receptors. For this reason 200 g male Sprague-Dawley rats received daily i.p. injections of PTU or T4. Levels of TRH and TRH-like peptides were measured 0, 2 h or 1, 2, 3, or 4 days later. Rapid increases or decreases in TRH and TRH-like peptide levels were observed in response to PTU and T4 treatments in various brain regions involved in mood regulation. Significant effects were measured within 2 h of T4 injection. Nuclear T3 receptor-mediated changes in gene expression altering translation, post-translational processing and constitutive release of peptides require more than 2 h. We conclude that non-genomic mechanisms may contribute to the psychiatric effects of thyroid disease and thyroid hormone adjuvant treatment for major depression.
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Affiliation(s)
- A Eugene Pekary
- Research Service, VA Greater Los Angeles Healthcare System, University of California, Bldg. 114, Rm. 229, 11301 Wilshire Blvd., Los Angeles, CA 90073, USA.
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Morrish F, Buroker NE, Ge M, Ning XH, Lopez-Guisa J, Hockenbery D, Portman MA. Thyroid hormone receptor isoforms localize to cardiac mitochondrial matrix with potential for binding to receptor elements on mtDNA. Mitochondrion 2006; 6:143-8. [PMID: 16730242 DOI: 10.1016/j.mito.2006.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 04/13/2006] [Accepted: 04/21/2006] [Indexed: 11/29/2022]
Abstract
Thyroid hormone (T(3)) rapidly promotes both nuclear and mitochondrial DNA transcription in cardiomyocytes, suggesting that T3 directly binds and activates mitochondrial genes. We showed for the first time mitochondrial localization for multiple TRalpha isoforms in heart, including truncated versions. Additionally, we demonstrated novel mitochondrial localization for versions of TRalpha(2), the dominant negative isoform lacking a functional ligand-binding domain. We also confirmed by electromobility shift assays, that TRalpha(2) in mitochondrial extracts binds to thyroid receptor response elements present in the 12S rRNA (DRO) and D-loop region (DR2) of mitochondrial DNA. Thus, TRalpha isoforms may directly regulate T(3) responses at mtDNA in the heart.
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Affiliation(s)
- Fionnuala Morrish
- Children's Hospital and Regional Medical Center, Seattle, WA 98105, USA
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28
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Li YL, Litten C, Koehler KF, Mellström K, Garg N, Garcia Collazo AM, Färnegård M, Grynfarb M, Husman B, Sandberg J, Malm J. Thyroid receptor ligands. Part 4: 4′-amido bioisosteric ligands selective for the thyroid hormone receptor beta. Bioorg Med Chem Lett 2006; 16:884-6. [PMID: 16303304 DOI: 10.1016/j.bmcl.2005.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2005] [Revised: 11/01/2005] [Accepted: 11/02/2005] [Indexed: 10/25/2022]
Abstract
Based on the examination of the X-ray crystallographic structures of the LBD of TRalpha and TRbeta in complex with KB-141 (2), a number of novel 4'-hydroxy bioisosteric thyromimetics were prepared. Optimal affinity and beta-selectivity (33 times), was found with a medium-sized alkyl-substituted amido group; iso-butyl (12c). It can be concluded that bioisosteric replacements of the 4'-hydroxy position represent a new promising class of TRbeta-selective synthetic thyromimetics.
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Affiliation(s)
- Yi-Lin Li
- Karo Bio AB, Novum, Huddinge S-141 57, Sweden
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29
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Figueira ACM, Dias SMG, Santos MAM, Apriletti JW, Baxter JD, Webb P, Neves FAR, Simeoni LA, Ribeiro RCJ, Polikarpov I. Human Thyroid Receptor Forms Tetramers in Solution, Which Dissociate Into Dimers Upon Ligand Binding. Cell Biochem Biophys 2006; 44:453-62. [PMID: 16679533 DOI: 10.1385/cbb:44:3:453] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 11/11/2022]
Abstract
Thyroid hormone nuclear receptors (TRs) bind to DNA and activate transcription as heterodimers with the retinoid X receptor (RXR) or as homodimers or monomers. RXR also binds to DNA and activates transcription as homodimers but can, in addition, self-associate into homotetramers in the absence of ligand and DNA templates. It is thought that homotetramer formation serves to sequester excess RXRs into an inactive pool within the cell. Here, we report systematic studies of the multimeric state of a recombinant human TRbeta1 truncation (hTRbeta1deltaAB) that encompasses the complete DNA binding domain and ligand binding domain in solution. Native gel electrophoresis, chemical crosslinking, gel filtration, and dynamic light scattering experiments reveal that hTRbeta1deltaAB forms a mixture of monomers, dimers, and tetramers. Like RXR, increasing protein concentration shifts the equilibrium between TR multimers toward tetramer formation, whereas binding of cognate thyroid hormone leads to dissociation of tetramers and increased formation of dimers. This work represents the first evidence that apo-hTRbeta1 forms homotetramers. The findings raise the possibility that tetramer formation provides an additional, and previously unsuspected, level of control of TR activity and that the capacity for homotetramer formation may be more widespread in the nuclear receptor family than previously thought.
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Affiliation(s)
- Ana C M Figueira
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
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30
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Martínez L, Webb P, Polikarpov I, Skaf MS. Molecular Dynamics Simulations of Ligand Dissociation from Thyroid Hormone Receptors: Evidence of the Likeliest Escape Pathway and Its Implications for the Design of Novel Ligands. J Med Chem 2005; 49:23-6. [PMID: 16392786 DOI: 10.1021/jm050805n] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Steered molecular dynamics simulations of ligand dissociation from Thyroid hormone receptors indicate that dissociation is favored via rearrangements in a mobile part of the LBD comprising H3, the loop between H1 and H2, and nearby beta-sheets, contrary to current models in which the H12 is mostly involved. Dissociation is facilitated in this path by the interaction of the hydrophilic part of the ligand with external water molecules, suggesting strategies to enhance ligand binding affinity.
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Affiliation(s)
- Leandro Martínez
- Instituto de Química, Universidade Estadual de Campinas - UNICAMP Cx. P. 6154, Campinas, SP 13084-862, Brazil
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31
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Zhang Y, Conrad AH, Conrad GW. Detection and quantification of 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine by electrospray ionization tandem mass spectrometry. J Am Soc Mass Spectrom 2005; 16:1781-6. [PMID: 16182556 DOI: 10.1016/j.jasms.2005.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Revised: 06/23/2005] [Accepted: 06/24/2005] [Indexed: 05/04/2023]
Abstract
A novel and rapid method for identifying and quantifying 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3; reverse T3) has been introduced using electrospray ionization tandem mass spectrometry (ESI-MS/MS). MS(2) spectra in either negative ionization mode or positive ionization mode can be used to differentiate T3 and rT3. Quantification of the T3 and rT3 isomers under the negative ionization mode is also achieved without prior separation by HPLC.
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Affiliation(s)
- Yuntao Zhang
- Division of Biology, Kansas State University, Ackert Hall, Manhattan, KS 66506-4901, USA.
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32
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Faergemann J, Wahlstrand B, Hedner T, Johnsson J, Neubert RHH, Nyström L, Maibach H. Pentane-1,5-diol as a percutaneous absorption enhancer. Arch Dermatol Res 2005; 297:261-5. [PMID: 16215760 DOI: 10.1007/s00403-005-0610-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 09/10/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
Propylene glycol (propane-1,2-diol) is the only diol widely used in dermatology. Pentane-1,5-diol is mainly used as a plasticizer in cellulose products and adhesives, in dental composites and in brake fluid compositions and as a preservative for grain. However, pentane-1,5-diol is also an effective solvent, water-binding substance, antimicrobial agent and preservative and may therefore replace several ingredients in a skin composition. The release of tri-iodothyroacetic acid (TRIAC) and percutaneous absorption of hydrocortisone and mometasone furoate with either pentane-1,5-diol or propane-1,2-diol and 2-methyl-pentane-2,4-diol (hexylene glycol), respectively, as enhancers was compared. The release of TRIAC was 21% higher when pentane-1,5-diol was used as an enhancer instead of propane-1,2-diol. The percutaneous absorption of hydrocortisone through the skin was increased 12 times with propane-1,2-diol compared to 4.4 times with pentane-1,5-diol. However, the percutaneous absorption of hydrocortisone into the skin was 50% higher with pentane-1,5-diol compared to propane-1,2-diol. There was no significant difference, between the original mometasone furoate cream, with 2-methyl-pentane-2,4-diol, and the new cream with pentane-1,5-diol in the amount of mometasone furoate that was absorbed into the skin and through the skin. However, the cosmetic properties of the new mometasone furoate cream was superior to the original mometasone furoate cream, for examples, no bad odour, more even texture, goes better into the skin and has less greasiness. Pentane-1,5-diol can be used as a technology platform, which adds a series of desirable properties to dermatological preparations and enhances product usability. This will result in improved formulations for a series of major and commonly used dermatological drugs. When used in pharmaceutical topical preparations, pentane-1,5-diol will increase the percutaneous absorption of the active substance and it is an efficient antimicrobial agent that will act as an effective preservative in topical formulations. Pentane-1,5-diol is cosmetically attractive, has low risk for skin and eye irritation compared to other diols, low toxicity risk and no bad odour.
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Affiliation(s)
- Jan Faergemann
- Department of Dermatology, Sahlgrenska University Hospital, SE-41345, Gothenburg, Sweden.
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33
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Martínez L, Sonoda MT, Webb P, Baxter JD, Skaf MS, Polikarpov I. Molecular dynamics simulations reveal multiple pathways of ligand dissociation from thyroid hormone receptors. Biophys J 2005; 89:2011-23. [PMID: 15980170 PMCID: PMC1366704 DOI: 10.1529/biophysj.105.063818] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Accepted: 06/09/2005] [Indexed: 11/18/2022] Open
Abstract
Nuclear receptor (NR) ligands occupy a pocket that lies within the core of the NR ligand-binding domain (LBD), and most NR LBDs lack obvious entry/exit routes upon the protein surface. Thus, significant NR conformational rearrangements must accompany ligand binding and release. The precise nature of these processes, however, remains poorly understood. Here, we utilize locally enhanced sampling (LES) molecular dynamics computer simulations to predict molecular motions of x-ray structures of thyroid hormone receptor (TR) LBDs and determine events that permit ligand escape. We find that the natural ligand 3,5,3'-triiodo-L-thyronine (T(3)) dissociates from the TRalpha1 LBD along three competing pathways generated through i), opening of helix (H) 12; ii), separation of H8 and H11 and the Omega-loop between H2 and H3; and iii), opening of H2 and H3, and the intervening beta-strand. Similar pathways are involved in dissociation of T(3) and the TRbeta-selective ligand GC24 from TRbeta; the TR agonist IH5 from the alpha- and beta-TR forms; and Triac from two natural human TRbeta mutants, A317T and A234T, but are detected with different frequencies in simulations performed with the different structures. Path I was previously suggested to represent a major pathway for NR ligand dissociation. We propose here that Paths II and III are also likely ligand escape routes for TRs and other NRs. We also propose that different escape paths are preferred in different situations, implying that it will be possible to design NR ligands that only associate stably with their cognate receptors in specific cellular contexts.
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Affiliation(s)
- Leandro Martínez
- Instituto de Química, Universidade Estadual de Campinas, Campinas SP 13084-862, Brazil
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34
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Maia AL, Kim BW, Huang SA, Harney JW, Larsen PR. Type 2 iodothyronine deiodinase is the major source of plasma T3 in euthyroid humans. J Clin Invest 2005; 115:2524-33. [PMID: 16127464 PMCID: PMC1190373 DOI: 10.1172/jci25083] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Accepted: 06/21/2005] [Indexed: 01/20/2023] Open
Abstract
The relative roles of the types 1 and 2 iodothyronine deiodinases (D1 and D2) in extrathyroidal 3,5,3'-triiodothyronine (T3) production in humans are unknown. We calculated the rate of thyroxine (T4) to T3 conversion by intact cells transiently expressing D1 or D2 at low (2 pM), normal (20 pM), and high (200 pM) free T4 concentrations. Deiodinase activities were then assayed in cell sonicates. The ratio of T3 production in cell sonicates (catalytic efficiency) was multiplied by the tissue activities reported in human liver (D1) and skeletal muscle (D2). From these calculations, we predict that in euthyroid humans, D2-generated T3 is 29 nmol/d, while that of D1-generated T3 is 15 nmol/d, from these major deiodinase-expressing tissues. The total estimated extrathyroidal T3 production, 44 nmol/d, is in close agreement with the 40 nmol T3/d based on previous kinetic studies. D2-generated T3 production accounts for approximately 71% of the peripheral T3 production in hypothyroidism, but D1 for approximately 67% in thyrotoxic patients. We also show that the intracellular D2-generated T3 has a greater effect on T3-dependent gene transcription than that from D1, which indicates that generation of nuclear T3 is an intrinsic property of the D2 protein. We suggest that impairment of D2-generated T3 is the major cause of the reduced T3 production in the euthyroid sick syndrome.
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Affiliation(s)
- Ana Luiza Maia
- Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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35
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Maia AL, Kim BW, Huang SA, Harney JW, Larsen PR. Type 2 iodothyronine deiodinase is the major source of plasma T3 in euthyroid humans. J Clin Invest 2005. [PMID: 16127464 DOI: 10.1172/jci25083.2524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023] Open
Abstract
The relative roles of the types 1 and 2 iodothyronine deiodinases (D1 and D2) in extrathyroidal 3,5,3'-triiodothyronine (T3) production in humans are unknown. We calculated the rate of thyroxine (T4) to T3 conversion by intact cells transiently expressing D1 or D2 at low (2 pM), normal (20 pM), and high (200 pM) free T4 concentrations. Deiodinase activities were then assayed in cell sonicates. The ratio of T3 production in cell sonicates (catalytic efficiency) was multiplied by the tissue activities reported in human liver (D1) and skeletal muscle (D2). From these calculations, we predict that in euthyroid humans, D2-generated T3 is 29 nmol/d, while that of D1-generated T3 is 15 nmol/d, from these major deiodinase-expressing tissues. The total estimated extrathyroidal T3 production, 44 nmol/d, is in close agreement with the 40 nmol T3/d based on previous kinetic studies. D2-generated T3 production accounts for approximately 71% of the peripheral T3 production in hypothyroidism, but D1 for approximately 67% in thyrotoxic patients. We also show that the intracellular D2-generated T3 has a greater effect on T3-dependent gene transcription than that from D1, which indicates that generation of nuclear T3 is an intrinsic property of the D2 protein. We suggest that impairment of D2-generated T3 is the major cause of the reduced T3 production in the euthyroid sick syndrome.
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Affiliation(s)
- Ana Luiza Maia
- Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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36
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Abstract
Deiodination is the foremost pathway of thyroid hormone metabolism not only in quantitative terms but also because thyroxine (T(4)) is activated by outer ring deiodination (ORD) to 3,3',5-triiodothyronine (T(3)), whereas both T(4) and T(3) are inactivated by inner ring deiodination (IRD) to 3,3',5-triiodothyronine and 3,3'-diiodothyronine, respectively. These reactions are catalyzed by three iodothyronine deiodinases, D1-3. Although they are homologous selenoproteins, they differ in important respects such as catalysis of ORD and/or IRD, deiodination of sulfated iodothyronines, inhibition by the thyrostatic drug propylthiouracil, and regulation during fetal and neonatal development, by thyroid state, and during illness. In this review we will briefly discuss recent developments in these different areas. These have resulted in the emerging view that the biological activity of thyroid hormone is regulated locally by tissue-specific regulation of the different deiodinases.
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Affiliation(s)
- George G J M Kuiper
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
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37
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Alvarez RMS, Cutin EH, Farías RN. Conformational Changes of 3,5,3′-Triiodo L-Thyronine Induced by Interactions with Phospholipid: Physiological Speculations. J Membr Biol 2005; 205:61-9. [PMID: 16283586 DOI: 10.1007/s00232-005-0763-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 07/23/2005] [Indexed: 11/25/2022]
Abstract
The conformational changes of 3,5,3'-triiodo L-thyronine induced by interaction with phospholipids were analyzed by Raman spectroscopy. The spectra were interpreted in terms of two conformers of this hormone in equilibrium in the lipid medium, depending on the orientation of the 3'-iodine with respect to the ring alpha. Theoretical geometry optimizations on both conformers in vacuo and in different solvents, together with the respective calculated energies support the experimental results. The presence of only one iodine atom in the phenolic ring allows assumption of a higher flexibility of 3,5,3'-triiodo L-thyronine and a better accommodation into the lipid medium compared to 3,5,3',5'-tetraiodo L-thyronine. The possible physiological implications of structural differences that appear in membrane models between 3,5,3'-triiodo L-thyronine and 3,5,3',5'-tetraiodo L-thyronine are discussed.
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Affiliation(s)
- R M S Alvarez
- Departamento de Bioquímica de la Nutritión, Instituto Superior de Investigaciones Biológicas (CONICET-UNT), Tucumán, Argentina
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38
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Couldwell AM, Thomas MC, Mitchell TW, Hulbert AJ, Blanksby SJ. Tandem mass spectrometry of deprotonated iodothyronines. Rapid Commun Mass Spectrom 2005; 19:2295-304. [PMID: 16021613 DOI: 10.1002/rcm.2061] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In order to assist with the development of more selective and sensitive methods for thyroid hormone analysis the [M-H]- anions of the iodothyronines T4, T3, rT3, (3,5)-T2 and the non-iodinated thyronine (T0) have been generated by negative ion electrospray mass spectrometry. Tandem mass spectra of these ions were recorded on a triple-quadrupole mass spectrometer and show a strong analogy with the fragmentation pathways of the parent compound, tyrosine. All iodothyronines also show significant abundances of the iodide anion in their tandem mass spectra, which represents an attractive target for multiple reaction monitoring (MRM) analysis, given that iodothyronines are the only iodine bearing endogenous molecules. Characteristic fragments are observed at m/z 359.7 and 604.5 for rT3 but are absent in the spectrum of T3, thus differentiating the two positional isomers. The striking difference in the fragmentation patterns of these regioisomeric species is attributed to the increased acidity of the phenol moiety in rT3 compared with T3.
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Affiliation(s)
- Alison M Couldwell
- Department of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia
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39
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Sandler B, Webb P, Apriletti JW, Huber BR, Togashi M, Cunha Lima ST, Juric S, Nilsson S, Wagner R, Fletterick RJ, Baxter JD. Thyroxine-thyroid hormone receptor interactions. J Biol Chem 2004; 279:55801-8. [PMID: 15466465 DOI: 10.1074/jbc.m410124200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thyroid hormone (TH) actions are mediated by nuclear receptors (TRs alpha and beta) that bind triiodothyronine (T(3), 3,5,3'-triiodo-l-thyronine) with high affinity, and its precursor thyroxine (T(4), 3,5,3',5'-tetraiodo-l-thyronine) with lower affinity. T(4) contains a bulky 5' iodine group absent from T(3). Because T(3) is buried in the core of the ligand binding domain (LBD), we have predicted that TH analogues with 5' substituents should fit poorly into the ligand binding pocket and perhaps behave as antagonists. We therefore examined how T(4) affects TR activity and conformation. We obtained several lines of evidence (ligand dissociation kinetics, migration on hydrophobic interaction columns, and non-denaturing gels) that TR-T(4) complexes adopt a conformation that differs from TR-T(3) complexes in solution. Nonetheless, T(4) behaves as an agonist in vitro (in effects on coregulator and DNA binding) and in cells, when conversion to T(3) does not contribute to agonist activity. We determined x-ray crystal structures of the TRbeta LBD in complex with T(3) and T(4) at 2.5-A and 3.1-A resolution. Comparison of the structures reveals that TRbeta accommodates T(4) through subtle alterations in the loop connecting helices 11 and 12 and amino acid side chains in the pocket, which, together, enlarge a niche that permits helix 12 to pack over the 5' iodine and complete the coactivator binding surface. While T(3) is the major active TH, our results suggest that T(4) could activate nuclear TRs at appropriate concentrations. The ability of TR to adapt to the 5' extension should be considered in TR ligand design.
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Affiliation(s)
- Ben Sandler
- Metabolic Research Unit and Diabetes Center, School of Medicine, University of California-San Francisco, 513 Parnassus Avenue, San Francisco, CA 94122-0540, USA
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40
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Nieminen P, Pyykönen T, Asikainen J, Mononen J, Mustonen AM. Effects of fasting and exogenous melatonin on annual rhythms in the blue fox (Alopex lagopus). Comp Biochem Physiol A Mol Integr Physiol 2004; 139:183-97. [PMID: 15528167 DOI: 10.1016/j.cbpb.2004.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Revised: 08/26/2004] [Accepted: 09/01/2004] [Indexed: 11/22/2022]
Abstract
The arctic fox (Alopex lagopus) is a winter-active inhabitant of the high arctic with extreme fluctuations in photoperiod and food availability. The blue fox is a semi-domesticated variant of the wild arctic fox reared for the fur industry. In this study, 48 blue foxes were followed for a year in order to determine the effects of exogenous melatonin and wintertime food deprivation on their reproductive and thyroid axes. Half of the animals were treated with continuous-release melatonin capsules in July 2002, and in November-January, the animals were divided into three groups and either fed continuously or fasted for one or two 22-day periods. Food deprivation decreased the plasma triiodothyronine and thyroxine concentrations probably in order to preserve energy due to a decreased metabolic rate. The same was observed in the plasma testosterone levels of the males but not in the plasma estradiol concentrations of the females. Exogenous melatonin advanced the autumn moult and seasonal changes in the voluntary food intake. It also advanced the onset of the testosterone peak in the males. The plasma estradiol levels of the females were unaffected, but the progesterone levels peaked more steeply in the sham-operated females. Melatonin exerted a strong influence not only on the reproductive axis of the males but also on the seasonal food intake. The species seemed quite resistant to periodic involuntary food deprivation.
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Affiliation(s)
- Petteri Nieminen
- Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101, Finland.
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41
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Abstract
[reaction: see text] In a model beta-hairpin peptide, we have found that the favorable interaction of cross-strand aromatic rings can be enhanced by up to 1 kcal mol(-1) with halogen substituents. It appears that the polarizability of the halogen atoms accounts for the increase in stability and that there is a direct interaction between the N-terminal phenylalanine and the halogen atom. Thermal denaturation studies indicate that the interaction is enthalpically driven with an associated entropic cost. These findings have relevance to areas of molecular recognition and drug design.
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Affiliation(s)
- Chad D Tatko
- Department of Chemistry, CB 3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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42
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Hangeland JJ, Doweyko AM, Dejneka T, Friends TJ, Devasthale P, Mellström K, Sandberg J, Grynfarb M, Sack JS, Einspahr H, Färnegårdh M, Husman B, Ljunggren J, Koehler K, Sheppard C, Malm J, Ryono DE. Thyroid receptor ligands. Part 2: Thyromimetics with improved selectivity for the thyroid hormone receptor beta. Bioorg Med Chem Lett 2004; 14:3549-53. [PMID: 15177471 DOI: 10.1016/j.bmcl.2004.04.032] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Revised: 04/09/2004] [Accepted: 04/10/2004] [Indexed: 12/01/2022]
Abstract
A set of thyromimetics having improved selectivity for TR-beta1 were prepared by replacing the 3'-isopropyl group of 2 and 3 with substituents having increased steric bulk. From this limited SAR study, the most potent and selective compounds identified were derived from 2 and contained a 3'-phenyl moiety bearing small hydrophobic groups meta to the biphenyl link. X-ray crystal data of 15c complexed with TR-beta1 LBD shows methionine 442 to be displaced by the bulky R3' phenyl ethyl amide side chain. Movement of this amino acid side chain provides an expanded pocket for the bulky side chain while the ligand-receptor complex retains full agonist activity.
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Affiliation(s)
- Jon J Hangeland
- Pharmaceutical Research Institute, Bristol-Myers Squibb, Princeton, NJ 08543, USA.
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43
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Eneqvist T, Lundberg E, Karlsson A, Huang S, Santos CRA, Power DM, Sauer-Eriksson AE. High resolution crystal structures of piscine transthyretin reveal different binding modes for triiodothyronine and thyroxine. J Biol Chem 2004; 279:26411-6. [PMID: 15082720 DOI: 10.1074/jbc.m313553200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transthyretin (TTR) is an extracellular transport protein involved in the distribution of thyroid hormones and vitamin A. So far, TTR has only been found in vertebrates, of which piscine TTR displays the lowest sequence identity with human TTR (47%). Human and piscine TTR bind both thyroid hormones 3,5,3'-triiodo-l-thyronine (T(3)) and 3,5,3',5'-tetraiodo-l-thyronine (thyroxine, T(4)). Human TTR has higher affinity for T(4) than T(3), whereas the reverse holds for piscine TTR. X-ray structures of Sparus aurata (sea bream) TTR have been determined as the apo-protein at 1.75 A resolution and bound to ligands T(3) and T(4), both at 1.9 A resolution. The apo structure is similar to human TTR with structural changes only at beta-strand D. This strand forms an extended loop conformation similar to the one in chicken TTR. The piscine TTR.T(4) complex shows the T(4)-binding site to be similar but not identical to human TTR, whereas the TTR.T(3) complex shows the I3' halogen situated at the site normally occupied by the hydroxyl group of T(4). The significantly wider entrance of the hormone-binding channel in sea bream TTR, in combination with its narrower cavity, provides a structural explanation for the different binding affinities of human and piscine TTR to T(3) and T(4).
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Affiliation(s)
- Therese Eneqvist
- Umea Centre for Molecular Pathogenesis, Umea University, SE-901 87 Umea, Sweden
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Grover GJ, Egan DM, Sleph PG, Beehler BC, Chiellini G, Nguyen NH, Baxter JD, Scanlan TS. Effects of the thyroid hormone receptor agonist GC-1 on metabolic rate and cholesterol in rats and primates: selective actions relative to 3,5,3'-triiodo-L-thyronine. Endocrinology 2004; 145:1656-61. [PMID: 14701670 DOI: 10.1210/en.2003-0973] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Current drug therapies for obesity are ineffective, and existing treatments for lipid disorders can be further improved. Thyroid hormones affect both conditions, although currently available nonselective thyromimetics are not clinically useful for such treatment due to cardiac side effects. Recent studies suggest that thyroid hormone receptor subtype beta (TRbeta) selective agonists have a profile in which cholesterol can be reduced with minimal tachycardia. The purpose of this study was to determine whether modest (5-10%) increases in metabolic rate could also be observed with minimal tachycardia after TRbeta stimulation. For these studies, the TRbeta selective agonist, GC-1, was used to assess selectivity for lipid-lowering and metabolic rate changes relative to tachycardia. Studies in cholesterol-fed rats (7 d treatment) showed that GC-1 reduced cholesterol (ED(50) = 190 nmol/kg x d) approximately 30 times more potently than it induced tachycardia (ED(15) = 5451 nmol/kg x d). T(3) showed no potency difference between cholesterol lowering and tachycardia. GC-1 showed approximately 10-fold selectivity for increasing metabolic rate (ED(5) = 477 nmol/kg x d) relative to tachycardia compared with T(3), which showed no selectivity. In cynomolgus monkeys treated for 7 d, significant cholesterol-lowering and lipoprotein (a) reduction was noted for both T(3) and GC-1, whereas no tachycardia was observed for GC-1, unlike T(3). T(3) and GC-1 caused a significant (approximately 4%) reduction in body weight in these animals. Therefore, selective TRbeta activation may be a potentially usefully treatment for obesity and reduction of low density lipoprotein cholesterol and reduction of the atherogenic risk factor lipoprotein (a).
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Affiliation(s)
- Gary J Grover
- Metabolic and Cardiovascular Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Pennington, New Jersey 08534, USA.
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Chen C, Staudinger JL, Klaassen CD. Nuclear receptor, pregname X receptor, is required for induction of UDP-glucuronosyltranferases in mouse liver by pregnenolone-16 alpha-carbonitrile. Drug Metab Dispos 2003; 31:908-15. [PMID: 12814968 DOI: 10.1124/dmd.31.7.908] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to determine the role of pregnane X receptor (PXR) in the induction of UDP-glucuronosyltransferases (UGTs) by pregnenolone-16 alpha-carbonitrile (PCN). Four- to six-month-old male wild-type and PXR-null mice received control or PCN-treated (1500 ppm) diet for 21 days. On day 22, livers were taken to prepare microsomes and total RNA to determine UGT activity and mRNA levels, respectively. In wild-type mice, PCN treatment significantly increased UGT activities toward bilirubin, 1-naphthol, chloramphenicol, thyroxine, and triiodothyronine. On control diet, the UGT activities toward the above substrates (except for 1-naphthol) in the PXR-null mice were significantly higher than those of wild-type mice. However, UGT activities in PXR-null mice were not increased by PCN. In agreement with the above findings, mRNA levels of mouse Ugt1a1 and Ugt1a9, which are involved in the glucuronidation of bilirubin and phenolic compounds, were increased about 100% in wild-type mice following PCN treatment, whereas the expression of Ugt1a2, 1a6, and 2b5 was not affected. In contrast, PCN treatment had no effect on the mRNA levels of these UGTs in PXR-null mice. Taken together, these results indicate that PCN treatment induces glucuronidation in mouse liver, and that PXR regulates constitutive and PCN-inducible expression of some UGTs.
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Affiliation(s)
- Chuan Chen
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
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Kvícala J, Zamrazil V. Effect of iodine and selenium upon thyroid function. Cent Eur J Public Health 2003; 11:107-13. [PMID: 12884559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
Iodine is an essential element with unique role in organism: it is indispensable component of thyroid hormones. After binding with specific nuclear receptor, T3/T4 induce transcription of genetic code via mRNA and regulate proteosynthesis in most tissues. Thyroid hormones regulate rate of metabolic processes and consequently development of organism. Czech Republic was in past typical region with moderate to severe iodine deficiency. Therefore epidemiological survey was started in randomly selected samples of peoples. Thereafter a complex program of improving iodine supply was realized. Prompt effects of this changes were recorded, namely increase of ioduria and decrease of thyroid volume. Essential trace element selenium has a fundamental importance to the cell and body metabolism regulation by thyroid hormones. Activities of selenoenzymes deiodinases lead to the activation of prohormone T4 to active hormone T3 and the inactivation of T3 and of T4, as well. There is unfortunately moderate to mild Se deficit in the CR. Average serum Se concentrations for the populations from 6 to 65 years are in the regions of the CR between 42 and 62 micrograms/l and urine Se values are between 8 and 15 micrograms/l. We have found statistically significant correlations among indexes of selenium status and indexes of thyroid hormone metabolism and function. Especially dangerous are concomitant deficiencies of both key elements for thyroid hormone metabolism--I and Se--from the point of thyroid hormone regulative functions.
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Affiliation(s)
- J Kvícala
- Institute of Endocrinology, Národní 8, 116 94 Prague, Czech Republic.
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Nishimura T, Taji H, Harada N. Absolute configuration of the thyroid hormone analog KAT-2003 as determined by the1H NMR anisotropy method with a novel chiral auxiliary, M?NP acid. Chirality 2003; 16:13-21. [PMID: 14628295 DOI: 10.1002/chir.10301] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The absolute configuration of the chiral thyroid hormone analog KAT-2003 (+)-2, showing hypocholesterolemic activities, decreases of hepatic triglyceride contents with lowering cardiac side effects, and significant inhibitory effect for the second primary hepatocellular carcinoma, was determined as S by the (1)H NMR anisotropy method using a novel chiral auxiliary, 2-methoxy-2-(1-naphtyl)propionic acid (MalphaNP acid).
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Affiliation(s)
- Toshihiro Nishimura
- Central Research Laboratories, Kissei Pharmaceutical Co., Nagano-Pref., Japan
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Luft FC. Toxic thyroid adenoma and toxic multinodular goiter. J Mol Med (Berl) 2002; 78:657-60. [PMID: 11434717 DOI: 10.1007/s001090100187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- F C Luft
- Franz-Volhard-Klinik, Humboldt University of Berlin, Berlin-Buch, Germany.
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Wagner RL, Huber BR, Shiau AK, Kelly A, Cunha Lima ST, Scanlan TS, Apriletti JW, Baxter JD, West BL, Fletterick RJ. Hormone selectivity in thyroid hormone receptors. Mol Endocrinol 2001; 15:398-410. [PMID: 11222741 DOI: 10.1210/mend.15.3.0608] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Separate genes encode thyroid hormone receptor subtypes TRalpha (NR1A1) and TRbeta (NR1A2). Products from each of these contribute to hormone action, but the subtypes differ in tissue distribution and physiological response. Compounds that discriminate between these subtypes in vivo may be useful in treating important medical problems such as obesity and hypercholesterolemia. We previously determined the crystal structure of the rat (r) TRalpha ligand-binding domain (LBD). In the present study, we determined the crystal structure of the rTRalpha LBD in a complex with an additional ligand, Triac (3,5, 3'-triiodothyroacetic acid), and two crystal structures of the human (h) TRbeta receptor LBD in a complex with either Triac or a TRbeta-selective compound, GC-1 [3,5-dimethyl-4-(4'-hydroy-3'-isopropylbenzyl)-phenoxy acetic acid]. The rTRalpha and hTRbeta LBDs show close structural similarity. However, the hTRbeta structures extend into the DNA-binding domain and allow definition of a structural "hinge" region of only three amino acids. The two TR subtypes differ in the loop between helices 1 and 3, which could affect both ligand recognition and the effects of ligand in binding coactivators and corepressors. The two subtypes also differ in a single amino acid residue in the hormone-binding pocket, Asn (TRbeta) for Ser (TRalpha). Studies here with TRs in which the subtype-specific residue is exchanged suggest that most of the selectivity in binding derives from this amino acid difference. The flexibility of the polar region in the TRbeta receptor, combined with differential recognition of the chemical group at the 1-carbon position, seems to stabilize the complex with GC-1 and contribute to its beta-selectivity. These results suggest a strategy for development of subtype-specific compounds involving modifications of the ligand at the 1-position.
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Affiliation(s)
- R L Wagner
- Department of Biochemistry, University of California, San Francisco, California 94143, USA
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Abstract
Protein disulfide isomerase (PDI) is a folding assistant of the eukaryotic endoplasmic reticulum, but it also binds the hormones, estradiol, and 3,3',5-triiodo-l-thyronine (T(3)). Hormone binding could be at discrete hormone binding sites, or it could be a nonphysiological consequence of binding site(s) that are involved in the interaction PDI with its peptide and protein substrates. Equilibrium dialysis, fluorescent hydrophobic probe binding (4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS)), competition binding, and enzyme activity assays reveal that the hormone binding sites are distinct from the peptide/protein binding sites. PDI has one estradiol binding site with modest affinity (2.1 +/- 0.5 microm). There are two binding sites with comparable affinity for T(3) (4.3 +/- 1.4 microm). One of these overlaps the estradiol site, whereas the other binds the hydrophobic probe, bis-ANS. Neither estradiol nor T(3) inhibit the catalytic or chaperone activity of PDI. Although the affinity of PDI for the hormones estradiol and T(3) is modest, the high local concentration of PDI in the endoplasmic reticulum (>200 microm) would drive hormone binding and result in the association of a substantial fraction (>90%) of the hormones in the cell with PDI. High capacity, low affinity hormone sites may function to buffer hormone concentration in the cell and allow tight, specific binding to the true receptor while preserving a reasonable number of hormone molecules in the very small volume of the cellular environment.
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Affiliation(s)
- T P Primm
- Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030, USA
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