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Sanguinetti C, Minniti M, Susini V, Caponi L, Panichella G, Castiglione V, Aimo A, Emdin M, Vergaro G, Franzini M. The Journey of Human Transthyretin: Synthesis, Structure Stability, and Catabolism. Biomedicines 2022; 10:biomedicines10081906. [PMID: 36009453 PMCID: PMC9405911 DOI: 10.3390/biomedicines10081906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/03/2022] [Accepted: 08/04/2022] [Indexed: 12/19/2022] Open
Abstract
Transthyretin (TTR) is a homotetrameric protein mainly synthesised by the liver and the choroid plexus whose function is to carry the thyroid hormone thyroxine and the retinol-binding protein bound to retinol in plasma and cerebrospinal fluid. When the stability of the tetrameric structure is lost, it breaks down, paving the way for the aggregation of TTR monomers into insoluble fibrils leading to transthyretin (ATTR) amyloidosis, a progressive disorder mainly affecting the heart and nervous system. Several TTR gene mutations have been characterised as destabilisers of TTR structure and are associated with hereditary forms of ATTR amyloidosis. The reason why also the wild-type TTR is intrinsically amyloidogenic in some subjects is largely unknown. The aim of the review is to give an overview of the TTR biological life cycle which is largely unknown. For this purpose, the current knowledge on TTR physiological metabolism, from its synthesis to its catabolism, is described. Furthermore, a large section of the review is dedicated to examining in depth the role of mutations and physiological ligands on the stability of TTR tetramers.
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Affiliation(s)
- Chiara Sanguinetti
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
| | - Marianna Minniti
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
| | - Vanessa Susini
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
| | - Laura Caponi
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
| | - Giorgia Panichella
- “Health Science” Interdisciplinary Research Center, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
| | - Vincenzo Castiglione
- “Health Science” Interdisciplinary Research Center, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
| | - Alberto Aimo
- “Health Science” Interdisciplinary Research Center, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
- Cardiology Division, Fondazione Toscana Gabriele Monasterio, 56124 Pisa, Italy
| | - Michele Emdin
- “Health Science” Interdisciplinary Research Center, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
- Cardiology Division, Fondazione Toscana Gabriele Monasterio, 56124 Pisa, Italy
| | - Giuseppe Vergaro
- “Health Science” Interdisciplinary Research Center, Scuola Superiore Sant’Anna, 56127 Pisa, Italy
- Cardiology Division, Fondazione Toscana Gabriele Monasterio, 56124 Pisa, Italy
| | - Maria Franzini
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
- Correspondence:
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Reiner BC, Crist RC, Borner T, Doyle RP, Hayes MR, De Jonghe BC. Single nuclei RNA sequencing of the rat AP and NTS following GDF15 treatment. Mol Metab 2021; 56:101422. [PMID: 34942400 PMCID: PMC8749158 DOI: 10.1016/j.molmet.2021.101422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 11/30/2021] [Accepted: 12/16/2021] [Indexed: 12/04/2022] Open
Abstract
Objective Growth differentiation factor 15 (GDF15) is known to play a role in feeding, nausea, and body weight, with action through the GFRAL-RET receptor complex in the area postrema (AP) and nucleus tractus solitarius (NTS). To further elucidate the underlying cell type-specific molecular mechanisms downstream of GDF15 signaling, we used a single nuclei RNA sequencing (snRNAseq) approach to profile AP and NTS cellular subtype-specific transcriptomes after systemic GDF15 treatment. Methods AP and NTS micropunches were used for snRNAseq from Sprague Dawley rats 6 h following GDF15 or saline injection, and Seurat was used to identify cellular subtypes and cell type-specific alterations in gene expression that were due to the direct and secondary effects of systemic GDF15 treatment. Results Using the transcriptome profile of ∼35,000 individual AP/NTS nuclei, we identified 19 transcriptomically distinct cellular subtypes, including a single population Gfral and Ret positive excitatory neurons, representing the primary site of action for GDF15. A total of ∼600 cell type-specific differential expression events were identified in neurons and glia, including the identification of transcriptome alterations specific to the direct effects of GDF15 in the Gfral-Ret positive excitatory neurons and shared transcriptome alterations across neuronal and glial cell types. Downstream analyses identified shared and cell type-specific alterations in signaling pathways and upstream regulatory mechanisms of the observed transcriptome alterations. Conclusions These data provide a considerable advance in our understanding of AP and NTS cell type-specific molecular mechanisms associated with GDF15 signaling. The identified cellular subtype-specific regulatory mechanism and signaling pathways likely represent important targets for future pharmacotherapies. GDF15 directly alters transcription in Gfral- and Ret-positive excitatory neurons. GDF15 indirectly alters transcription in other neuronal and glial populations. Cell type-specific expression changes identify regulatory and signaling mechanisms.
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Affiliation(s)
- Benjamin C Reiner
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
| | - Richard C Crist
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Tito Borner
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104; Department of Biobehavioral Health Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Robert P Doyle
- Syracuse University, Department of Chemistry, 111 College Place, Syracuse, New York 13244
| | - Matthew R Hayes
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104; Department of Biobehavioral Health Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Bart C De Jonghe
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104; Department of Biobehavioral Health Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
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Weiss JM, Jones B, Koekkoek J, Bignert A, Lamoree MH. Per- and polyfluoroalkyl substances (PFASs) in Swedish household dust and exposure of pet cats. Environ Sci Pollut Res Int 2021; 28:39001-39013. [PMID: 33745045 PMCID: PMC8310504 DOI: 10.1007/s11356-021-13343-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 03/03/2021] [Indexed: 06/12/2023]
Abstract
Per- and polyfluoroalkyl substances (PFASs) are used in a wide range of products and have been found ubiquitously in our indoor environment, and there is evidence that exposure to PFAS can lead to adverse endocrine effects, such as thyroid hormone disruption. Pet cats have a high dust intake due to their grooming behavior and have been shown to be a suitable sentinel species for assessment of toddler's exposure. Here we used paired household dust (n=46) and cat serum (n=27) samples to establish whether dust is a relevant exposure pathway to PFASs. An analytical method for PFAS analysis was optimized using a low volume of cat serum samples, combining solid-phase extraction and online sample cleanup. Dust was extracted with methanol by sonication and cleaned up by addition of active carbon. In total, 27 PFASs were analyzed by liquid chromatography/mass spectrometry analysis. The correlation between PFAS levels in dust and serum, serum lipids and thyroid hormone levels, and PFAS levels in dust between different rooms were statistically evaluated. PFOS and PFDA could be quantified in all cat serum samples (median 2300 pg/mL and 430 pg/mL, respectively), followed by PFOA (median 1100 pg/mL), quantified in 96% of the samples. The levels of 6:2 and 8:2 diPAPs were determined in 65% and 92% of the serum samples, respectively, and were an order of magnitude lower (1.4-160 pg/mL). Household dust on the other hand was dominated by 6:2 and 8:2 diPAPs, with a median of 65 ng/g dust and 49 ng/g dust, respectively. PFOS (median 13 ng/g dust) and PFOA (median 9 ng/g dust) were quantified in 93% of the dust samples. Only eight PFASs were detected (>LOD) in at least 50% of the samples of both matrices and could be paired. Significant correlations between cat serum and dust were found for PFOA (rS=0.32, p<0.049) and PFUnDA (rS=0.55, p<0.001). Significant positive correlations were found between serum total thyroxine (rS=0.11, p<0.05) and PFNA and between serum cholesterol and PFHpA (rS=0.46, p<0.01), PFUnDA (rS=0.40, p<0.05), PFDoDA (rS=0.44, p<0.01), and sum PFAS (rS=0.48, p<0.01). In conclusion, this study confirmed that dust is a relevant exposure pathway for the ingestion of some PFASs for cats, and the serum levels of PFASs could be of relevance for the cat's health.
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Affiliation(s)
- Jana M Weiss
- Department of Environmental Science, Stockholm University, Svante Arrheniusväg 12, 10691, Stockholm, Sweden.
| | - Bernt Jones
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Box 7054, 75007, Uppsala, Sweden
| | - Jacco Koekkoek
- Department Environment & Health, Vrije Universiteit, De Boelelaan 1087, 1081HV, Amsterdam, The Netherlands
| | - Anders Bignert
- Department of Environmental Science, Stockholm University, Svante Arrheniusväg 12, 10691, Stockholm, Sweden
| | - Marja H Lamoree
- Department Environment & Health, Vrije Universiteit, De Boelelaan 1087, 1081HV, Amsterdam, The Netherlands
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Roy MA, Duche PR, Timme-Laragy AR. The sulfate metabolite of 3,3'-dichlorobiphenyl (PCB-11) impairs Cyp1a activity and increases hepatic neutral lipids in zebrafish larvae (Danio rerio). Chemosphere 2020; 260:127609. [PMID: 32693259 PMCID: PMC7530052 DOI: 10.1016/j.chemosphere.2020.127609] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 04/29/2020] [Revised: 07/02/2020] [Accepted: 07/03/2020] [Indexed: 05/25/2023]
Abstract
The environmental contaminant 3,3'-dichlorobiphenyl (PCB-11) is widely detected in environmental samples, and this parent compound along with its metabolites 4-OH-PCB-11 and 4-PCB-11-Sulfate are detected in human serum. Our previous research in zebrafish (Danio rerio) embryos shows exposure to 20 μM PCB-11 inhibits Cyp1a enzyme activity and perturbs lipid metabolism pathways. In this study, wildtype AB embryos underwent acute exposures from 1 to 4 days post fertilization (dpf) to 0.002-20 μM 4-OH-PCB-11 or 0.2-20 μM 4-PCB-11-Sulfate, with and without co-exposures to 100 μg/L benzo[a]pyrene (B[a]P) or 5 nM 3,3',4,4',5-pentachlorobiphenyl (PCB-126), and were assessed for in vivo EROD activity and morphometrics. Chronic exposures from 1 to 15 dpf to assess lipid accumulation using Oil-Red-O staining were also conducted with 0.2 μM parent or metabolite compounds, alongside a co-exposure experiment of 0.002-0.2 μM 4-PCB-11-Sulfate and 10 μg/L B[a]P. For acute experiments, 2 and 20 μM 4-OH-PCB-11 was lethal but no Cyp1a or morphological effects were observed at lower concentrations; 20 μM 4-PCB-11-Sulfate significantly lowered the Cyp1a activity of B[a]P and PCB-126 but did not alter morphological development. For chronic experiments, 0.2 μM 4-PCB-11-Sulfate significantly increased lipid accumulation 30% in single exposures and 44% in co-exposures with B[a]P. Further long-term studies would better elucidate the effects of this contaminant, particularly in the context of environmentally-relevant mixtures.
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Affiliation(s)
- Monika A Roy
- Department of Environmental Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Perseverance R Duche
- Department of Environmental Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Alicia R Timme-Laragy
- Department of Environmental Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
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Gaum PM, Gube M, Esser A, Schettgen T, Quinete N, Bertram J, Putschögl FM, Kraus T, Lang J. Depressive Symptoms After PCB Exposure: Hypotheses for Underlying Pathomechanisms via the Thyroid and Dopamine System. Int J Environ Res Public Health 2019; 16:E950. [PMID: 30884813 DOI: 10.3390/ijerph16060950] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 03/12/2019] [Accepted: 03/13/2019] [Indexed: 11/30/2022]
Abstract
Polychlorinated biphenyls’ (PCB) exposure has been reported to be associated with depressive symptoms, which is correlated to lower dopamine- (DA) and thyroxine-concentrations (T4). T4 is necessary for DA-synthesis and it binds to transthyretin (TTR) being transported into the brain. PCBs can displace T4 by binding to TTR itself, being transported into the brain and disturbing DA-synthesis, where depressive symptoms might occur. Consequently, the free T4-concentration (fT4) increases when PCBs bind to TTR. The interaction of PCBs with fT4 and its associations with the main DA metabolite, homovanillic acid (HVA), and depressive symptoms were investigated. In total, 116 participants (91.6% men) were investigated, who took part in three annual examinations (t1–t3) of the HELPcB health surveillance program. Blood was collected for measuring PCBs, hydroxy PCBs (OH-PCBs), and fT4 and urine for HVA. Depressive Symptoms were assessed with a standardized questionnaire. Interactions were tested cross-sectionally with multiple hierarchical regressions and longitudinally with mixed effect models. Related to HVA, an interaction was cross-sectionally found for lower-chlorinated PCBs (LPCBs) and dioxin-like PCBs (dlPCBs); longitudinally only for LPCBs. Related to depressive symptoms, the interaction was found for LPCBs, dlPCBs, and OH-PCBs; longitudinally again only for LPCBs. The results give first hints that a physiological process involving the thyroid and DA system is responsible for depressive symptoms after PCB exposure.
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Abstract
Transthyretin (TTR) related cardiomyopathy is an underdiagnosed cause of heart failure but is increasingly recognized in various settings - from patients admitted with heart failure to symptomatic aortic stenosis - and is rapidly becoming the most frequent form of systemic amyloidosis. Following the recent publication of the landmark ATTR-ACT trial that showed tafamidis to be the first treatment to improve survival in patients with TTR-related cardiac amyloidosis and heart failure, we reviewed the drug's rationale, characteristics and evidence supporting its use in TTR amyloidosis.
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Affiliation(s)
- Massimiliano Lorenzini
- University College London Institute for Cardiovascular Science & Barts Heart Centre, St Bartholomew's Hospital, London, UK.,Cardiology, Department of Experimental, Diagnostic & Specialty Medicine, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | - Perry M Elliott
- University College London Institute for Cardiovascular Science & Barts Heart Centre, St Bartholomew's Hospital, London, UK
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Affiliation(s)
- Julian T. Brennecke
- Department of Theoretical and Computational Biophysics, Computational Biomolecular, Dynamics Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Bert L. de Groot
- Department of Theoretical and Computational Biophysics, Computational Biomolecular, Dynamics Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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Zhang N, Bi S. Effects of physical exercise on food intake and body weight: Role of dorsomedial hypothalamic signaling. Physiol Behav 2018; 192:59-63. [DOI: 10.1016/j.physbeh.2018.03.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 03/10/2018] [Accepted: 03/15/2018] [Indexed: 12/19/2022]
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Gutleb AC, Cambier S, Serchi T. Impact of Endocrine Disruptors on the Thyroid Hormone System. Horm Res Paediatr 2018; 86:271-278. [PMID: 26771660 DOI: 10.1159/000443501] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/14/2015] [Indexed: 11/19/2022] Open
Abstract
The thyroid hormone (TH) system plays a central role in central physiological processes of many species, including mammals and humans, ranging from growth and cell differentiation, energy metabolism, thermoregulation and phasing of hibernation or annual movements of migratory species, metamorphosis from larvae to adult forms, brain development, reproduction, or the cardiovascular system. Several chemicals are known to be TH-disrupting compounds (THDCs) and have been shown to interact with virtually all elements of TH homeostasis such as feedback mechanisms with the hypothalamus-pituitary axis, TH synthesis, TH storage and release from the thyroid gland, transport protein binding and TH distribution in tissues and organs, cellular TH uptake, intracellular TH metabolism, and TH receptor binding. Therefore, chemicals interfering with the TH homeostasis have the potential to interact with many of these important processes, and especially early-life stage exposure results in permanent alterations of tissue organization and homeostatic regulation of adaptive processes. This is not only of theoretical importance as the reported plasma concentrations of THDCs in human plasma fall well within the range of reported in vitro effect concentrations, and this is of even higher importance as the developing fetus and young children are in a sensitive developmental stage.
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Affiliation(s)
- Arno C Gutleb
- Environmental Health Group, Life Cycle Sustainability and Risk Assessment (LiSRA) Unit, Environmental Research and Innovation (ERIN) Department, Luxembourg Institute of Science and Technology (LIST), Esch/Alzette, Luxembourg
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Saha S, Chakraborty S, Bhattacharya A, Biswas A, Ain R. MicroRNA regulation of Transthyretin in trophoblast differentiation and Intra-Uterine Growth Restriction. Sci Rep 2017; 7:16548. [PMID: 29185488 PMCID: PMC5707432 DOI: 10.1038/s41598-017-16566-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 11/14/2017] [Indexed: 02/07/2023] Open
Abstract
Placental trophoblast cells produce various cytokines, transporters vital to normal embryogenesis. Transthyretin (TTR) aids trans-placental passage of maternal thyroxin (TH) to fetal circulation. Inadequate TH delivery leads to developmental abnormality. Regulation of TTR biosynthesis in placenta is critical for normal embryo development. We showed here that TTR transcripts were expressed more in fetal placenta. Using bioinformatic analysis and confirmation with dual-luciferase reporter assays, we found that miR-200a-3p and miR-141-3p inhibited TTR expression by directly binding to the 3'UTR of TTR, which is reversed by mutation in the microRNA binding site. Differentiation of human trophoblast BeWo cells was associated with decreased TTR transcript and protein levels with concomitant increase in the levels of both microRNAs. Interestingly, ectopic overexpression of the microRNA mimics abrogated thyroxin uptake by BeWo cells, which was reversed by the corresponding inhibitors. Furthermore, in a rat model of intra-uterine growth restriction (IUGR), TTR expression decreased significantly in placenta with reciprocal rise in miR-141-3p but not 200a-3p. In human IUGR placenta, TTR transcript and protein levels were significantly lower associated with high expression of miR-141-3p but not 200a-3p. These data provides new insight into physiological role of miR-141-3p in regulating TTR during trophoblast differentiation and IUGR.
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Affiliation(s)
- Sarbani Saha
- Division of Cell Biology and Physiology, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India
| | - Shreeta Chakraborty
- Division of Cell Biology and Physiology, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India
| | | | - Arati Biswas
- Calcutta National Medical College, Kolkata, 700014, India
| | - Rupasri Ain
- Division of Cell Biology and Physiology, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India.
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Coelho T, Merlini G, Bulawa CE, Fleming JA, Judge DP, Kelly JW, Maurer MS, Planté-Bordeneuve V, Labaudinière R, Mundayat R, Riley S, Lombardo I, Huertas P. Mechanism of Action and Clinical Application of Tafamidis in Hereditary Transthyretin Amyloidosis. Neurol Ther 2016; 5:1-25. [PMID: 26894299 PMCID: PMC4919130 DOI: 10.1007/s40120-016-0040-x] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Indexed: 11/24/2022] Open
Abstract
Transthyretin (TTR) transports the retinol-binding protein-vitamin A complex and is a minor transporter of thyroxine in blood. Its tetrameric structure undergoes rate-limiting dissociation and monomer misfolding, enabling TTR to aggregate or to become amyloidogenic. Mutations in the TTR gene generally destabilize the tetramer and/or accelerate tetramer dissociation, promoting amyloidogenesis. TTR-related amyloidoses are rare, fatal, protein-misfolding disorders, characterized by formation of soluble aggregates of variable structure and tissue deposition of amyloid. The TTR amyloidoses present with a spectrum of manifestations, encompassing progressive neuropathy and/or cardiomyopathy. Until recently, the only accepted treatment to halt progression of hereditary TTR amyloidosis was liver transplantation, which replaces the hepatic source of mutant TTR with the less amyloidogenic wild-type TTR. Tafamidis meglumine is a rationally designed, non-NSAID benzoxazole derivative that binds with high affinity and selectivity to TTR and kinetically stabilizes the tetramer, slowing monomer formation, misfolding, and amyloidogenesis. Tafamidis is the first pharmacotherapy approved to slow the progression of peripheral neurologic impairment in TTR familial amyloid polyneuropathy. Here we describe the mechanism of action of tafamidis and review the clinical data, demonstrating that tafamidis treatment slows neurologic deterioration and preserves nutritional status, as well as quality of life in patients with early-stage Val30Met amyloidosis.
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Affiliation(s)
- Teresa Coelho
- Hospital de Santo António, Centro Hospitalar do Porto, Porto, Portugal.
| | - Giampaolo Merlini
- Foundation IRCCS Policlinico San Matteo, University of Pavia, Pavia, Italy
| | | | | | - Daniel P Judge
- Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | | | - Mathew S Maurer
- Columbia University College of Physicians and Surgeons, New York, NY, USA
| | | | | | | | | | | | - Pedro Huertas
- Massachusetts General and McLean Hospitals, Harvard Medical School, Boston, MA, USA
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Zheng F, Kim YJ, Moran TH, Li H, Bi S. Central transthyretin acts to decrease food intake and body weight. Sci Rep 2016; 6:24238. [PMID: 27053000 DOI: 10.1038/srep24238] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 03/22/2016] [Indexed: 01/09/2023] Open
Abstract
Transthyretin (TTR) is a blood and cerebrospinal fluid transporter of thyroxine and retinol. Gene expression profiling revealed an elevation of Ttr expression in the dorsomedial hypothalamus (DMH) of rats with exercise-induced anorexia, implying that central TTR may also play a functional role in modulating food intake and energy balance. To test this hypothesis, we have examined the effects of brain TTR on food intake and body weight and have further determined hypothalamic signaling that may underlie its feeding effect in rats. We found that intracerebroventricular (icv) administration of TTR in normal growing rats decreased food intake and body weight. This effect was not due to sickness as icv TTR did not cause a conditioned taste aversion. ICV TTR decreased neuropeptide Y (NPY) levels in the DMH and the paraventricular nucleus (P < 0.05). Chronic icv infusion of TTR in Otsuka Long-Evans Tokushima Fatty rats reversed hyperphagia and obesity and reduced DMH NPY levels. Overall, these results demonstrate a previously unknown anorectic action of central TTR in the control of energy balance, providing a potential novel target for treating obesity and its comorbidities.
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Abstract
BACKGROUND Impaired thyroid function is a common side effect of lithium medication. Recent data indicate that lithium exposure through drinking water, although providing much lower doses than the medication, may also affect thyroid hormone levels. However, the effects in susceptible groups like pregnant women are not known. METHODS In a population-based mother-child cohort in the Argentinean Andes (n = 194), an area with varying concentrations of lithium in the drinking water, we assessed lithium exposure repeatedly during pregnancy by measuring the concentrations in blood using inductively coupled plasma mass spectrometry. The markers of thyroid function included thyrotropin (TSH), free/total thyroxine (fT4/T4), free/total triiodothyronine (fT3/T3), thyroglobulin, and transthyretin in serum, sampled at the same time. Multiple potential confounders, including exposure to arsenic, cesium, and boron (elevated in water) as well as selenium and iodine (essential for thyroid function) were considered. RESULTS The lithium concentrations in blood [median 25 μg/L (0.0036 mmol/L); range 1.9-145 μg/L (0.000027-0.021 mmol/L)] correlated significantly with those in urine and drinking water (rs = 0.84, p < 0.001, and rs = 0.40, p < 0.001, respectively). Using linear quantile regression models, we found a positive association between blood lithium (log2 transformed) and TSH concentrations, particularly in the lowest percentiles of TSH (B = 0.20 mIU/L, [95% confidence interval 0.048-0.35] at the fifth percentile). We also found inverse associations of blood lithium with transthyretin, particularly at the highest percentiles, as well as with fT3 and T3, with less obvious variation across percentiles. Unexpectedly, blood cesium concentrations (median 111 μg/L, range 2.5-711 μg/L) were also inversely associated with fT3 and T3, particularly at the highest T3 percentiles, but not with TSH or transthyretin. Arsenic and boron exposure (also through drinking water) did not show any associations with the thyroid parameters. CONCLUSIONS The study supports previous findings that lithium exposure through drinking water may impair thyroid function. The results regarding cesium exposure through drinking water are new. During pregnancy, impaired thyroid function may be detrimental for fetal development. The findings reinforce the need for better control of drinking water, including bottled water, as well as a health-based guideline value.
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Affiliation(s)
- Florencia Harari
- Unit of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Matteo Bottai
- Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Esperanza Casimiro
- Atención Primaria de la Salud, Hospital Dr. Nicolás Cayetano Pagano, San Antonio de los Cobres, Salta, Argentina
| | - Brita Palm
- Unit of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Marie Vahter
- Unit of Metals and Health, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
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Haupt M, Blakeley MP, Fisher SJ, Mason SA, Cooper JB, Mitchell EP, Forsyth VT. Binding site asymmetry in human transthyretin: insights from a joint neutron and X-ray crystallographic analysis using perdeuterated protein. IUCrJ 2014; 1:429-38. [PMID: 25485123 PMCID: PMC4224461 DOI: 10.1107/s2052252514021113] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 09/22/2014] [Indexed: 05/12/2023]
Abstract
Human transthyretin has an intrinsic tendency to form amyloid fibrils and is heavily implicated in senile systemic amyloidosis. Here, detailed neutron structural studies of perdeuterated transthyretin are described. The analyses, which fully exploit the enhanced visibility of isotopically replaced hydrogen atoms, yield new information on the stability of the protein and the possible mechanisms of amyloid formation. Residue Ser117 may play a pivotal role in that a single water molecule is closely associated with the γ-hydrogen atoms in one of the binding pockets, and could be important in determining which of the two sites is available to the substrate. The hydrogen-bond network at the monomer-monomer interface is more extensive than that at the dimer-dimer interface. Additionally, the edge strands of the primary dimer are seen to be favourable for continuation of the β-sheet and the formation of an extended cross-β structure through sequential dimer couplings. It is argued that the precursor to fibril formation is the dimeric form of the protein.
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Affiliation(s)
- Melina Haupt
- Facility of Natural Sciences, Institute of Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, United Kingdom
- Institut Laue-Langevin, 71, avenue des Martyrs, Grenoble, CS 20156, France
- Partnership for Structural Biology, 71, avenue des Martyrs, Grenoble, CS 20156, France
| | - Matthew P. Blakeley
- Institut Laue-Langevin, 71, avenue des Martyrs, Grenoble, CS 20156, France
- Partnership for Structural Biology, 71, avenue des Martyrs, Grenoble, CS 20156, France
| | - Stuart J. Fisher
- Department of Molecular Biology, University of Salzburg, Billrothstrasse 11, Salzburg, 5020, Austria
- Diamond Light Source, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Sax A. Mason
- Institut Laue-Langevin, 71, avenue des Martyrs, Grenoble, CS 20156, France
| | - Jon B. Cooper
- Division of Medicine (Royal Free Campus), University College London, Rowland Hill Street, London NW3 2PF, United Kingdom
| | - Edward P. Mitchell
- Facility of Natural Sciences, Institute of Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, United Kingdom
- Partnership for Structural Biology, 71, avenue des Martyrs, Grenoble, CS 20156, France
- Business Development Office, European Synchrotron Radiation Facility, Grenoble, 38042, France
| | - V. Trevor Forsyth
- Facility of Natural Sciences, Institute of Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, United Kingdom
- Institut Laue-Langevin, 71, avenue des Martyrs, Grenoble, CS 20156, France
- Partnership for Structural Biology, 71, avenue des Martyrs, Grenoble, CS 20156, France
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15
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Grimm FA, Lehmler HJ, He X, Robertson LW, Duffel MW. Sulfated metabolites of polychlorinated biphenyls are high-affinity ligands for the thyroid hormone transport protein transthyretin. Environ Health Perspect 2013; 121:657-62. [PMID: 23584369 PMCID: PMC3672920 DOI: 10.1289/ehp.1206198] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [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: 10/29/2012] [Accepted: 04/11/2013] [Indexed: 05/20/2023]
Abstract
BACKGROUND The displacement of l-thyroxine (T4) from binding sites on transthyretin (TTR) is considered a significant contributing mechanism in polychlorinated biphenyl (PCB)-induced thyroid disruption. Previous research has discovered hydroxylated PCB metabolites (OH-PCBs) as high-affinity ligands for TTR, but the binding potential of conjugated PCB metabolites such as PCB sulfates has not been explored. OBJECTIVES We evaluated the binding of five lower-chlorinated PCB sulfates to human TTR and compared their binding characteristics to those determined for their OH-PCB precursors and for T4. METHODS We used fluorescence probe displacement studies and molecular docking simulations to characterize the binding of PCB sulfates to TTR. The stability of PCB sulfates and the reversibility of these interactions were characterized by HPLC analysis of PCB sulfates after their binding to TTR. The ability of OH-PCBs to serve as substrates for human cytosolic sulfotransferase 1A1 (hSULT1A1) was assessed by OH-PCB-dependent formation of adenosine-3',5'-diphosphate, an end product of the sulfation reaction. RESULTS All five PCB sulfates were able to bind to the high-affinity binding site of TTR with equilibrium dissociation constants (Kd values) in the low nanomolar range (4.8-16.8 nM), similar to that observed for T4 (4.7 nM). Docking simulations provided corroborating evidence for these binding interactions and indicated multiple high-affinity modes of binding. All OH-PCB precursors for these sulfates were found to be substrates for hSULT1A1. CONCLUSIONS Our findings show that PCB sulfates are high-affinity ligands for human TTR and therefore indicate, for the first time, a potential relevance for these metabolites in PCB-induced thyroid disruption.
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Affiliation(s)
- Fabian A Grimm
- Interdisciplinary Graduate Program in Human Toxicology, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, College of Public Health, The University of Iowa, Iowa City, Iowa 52246, USA
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16
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Buxbaum JN. Evaluation of tafamidis as first-line therapeutic agent for transthyretin familial amyloidotic polyneuropathy. Degener Neurol Neuromuscul Dis 2012; 2:165-173. [PMID: 30890886 DOI: 10.2147/dnnd.s24624] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Almost 100 mutations in the human transthyretin (TTR) gene cause the autosomal dominant disorders of familial amyloidotic polyneuropathy (FAP) and familial amyloidotic cardiomyopathy. While these have been clinically classified as separate disorders, the peripheral and autonomic nervous systems and the heart are frequently involved in the same patient. Deposition of amyloid derived from a kinetically or thermodynamically unstable mutant TTR precursor produces an ascending sensorimotor polyneuropathy with marked autonomic involvement. Since 1990, treatment has been liver transplantation from a donor carrying two wild-type TTR genes, providing a crude form of gene therapy. Multiple studies have shown that small molecules fitting in the T4-binding pocket of TTR can stabilize the molecule, reducing its capacity to release the fibril precursor. Tafamidis is the first molecule to be tested in a placebo-controlled trial in patients with TTR-associated FAP. While the trial did not achieve its primary endpoints, it did stabilize TTR in vivo and had a favorable effect on some aspects of disease progression, particularly when administered early in the course. It may represent an alternative to liver transplantation, particularly in patients with early disease related to the V30M mutation. Longer-term studies are required to determine whether it represents a stabilizing or remittive form of treatment.
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Affiliation(s)
- Joel N Buxbaum
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA,
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17
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Patel J, Landers KA, Mortimer RH, Richard K. Expression and uptake of the thyroxine-binding protein transthyretin is regulated by oxygen in primary trophoblast placental cells. J Endocrinol 2012; 212:159-67. [PMID: 22045754 DOI: 10.1530/joe-11-0348] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [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] [Indexed: 11/08/2022]
Abstract
Transplacental delivery of maternal thyroid hormones to the fetus, in particular thyroxine (T₄), is critical in ensuring normal fetal neurological development. The fetus relies on maternal T₄ till around 16 weeks gestation, but mechanisms of placental T₄ transport are not yet fully elucidated. Placenta produces, secretes and takes up the thyroid hormone-binding protein transthyretin (TTR). Many placental genes are regulated by oxygen levels, which are relatively low (1%) in the early first trimester, rising to 3% in the mid first trimester and 8% in the early second trimester and thereafter. We examined the expression and uptake of TTR in isolated primary human placental cytotrophoblast cells cultured under different oxygen concentrations (1, 3, 8, 21% O₂ and 200 μM desferrioxamine (DFO)) for 24 h. We observed sevenfold higher expression of TTR mRNA and protein levels at 1% O₂ than at 8 and 21% O₂. Significant increases were observed after culture at 3% O₂ and following DFO treatment. We observed significantly higher uptake of ¹²⁵I-TTR and Alexa-594-TTR when cells were cultured at 1 and 3% O₂ and in the presence of 200 μM DFO than at 8 and 21% O₂. When JEG-3 choriocarcinoma cells were transfected with TTR promoter reporter constructs, increased luciferase activity was measured in cells cultured at 1 and 3% O₂ in comparison to 8 and 21% O₂. We conclude that placental TTR expression and uptake is increased by the relative hypoxia observed in the first trimester of pregnancy, a time when materno-fetal T₄ transfer is the sole source of fetal T₄.
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Affiliation(s)
- J Patel
- School of Medicine, Royal Brisbane and Women's Hospital, The University of Queensland, Herston, Brisbane, Queensland 4029, Australia
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18
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Azevedo EPC, Pereira HM, Garratt RC, Kelly JW, Foguel D, Palhano FL. Dissecting the structure, thermodynamic stability, and aggregation properties of the A25T transthyretin (A25T-TTR) variant involved in leptomeningeal amyloidosis: identifying protein partners that co-aggregate during A25T-TTR fibrillogenesis in cerebrospinal fluid. Biochemistry 2011; 50:11070-83. [PMID: 22091638 DOI: 10.1021/bi201365r] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Deposition of amorphous aggregates and fibrils of transthyretin (TTR) in leptomeninges and subarachnoid vessels is a characteristic of leptomeningeal amyloidosis (LA), a currently untreatable cerebral angiopathy. Herein, we report the X-ray structure of the A25T homotetramer of TTR, a natural mutant described in a patient with LA. The structure of A25T-TTR is indistinguishable from that of wild-type TTR (wt-TTR), indicating that the difference in amyloidogenicity between A25T-TTR and wt-TTR cannot be ascribed to gross structural differences. Using pressure-induced dissociation of the tetramer, we show that A25T-TTR is 3 kcal/mol less stable than L55P-TTR, the most aggressive mutant of TTR described to date. After incubation for 15 days at 37 °C (pH 7.3), A25T-TTR forms mature amyloid fibrils. To mimic the environment in which TTR aggregates, we investigated aggregation in cerebrospinal fluid (CSF). Unlike L55P-TTR, A25T-TTR rapidly forms amyloid aggregates in CSF that incorporated several protein partners. Utilizing a proteomics methodology, we identified 19 proteins that copurified with A25T-TTR amyloid fibrils. We confirmed the presence of proteins previously identified to be associated with TTR aggregates in biopsies of TTR amyloidosis patients, such as clusterin, apolipoprotein E, and complement proteins. Moreover, we identified novel proteins, such as blood coagulation proteins. Overall, our results revealed the in vitro characterization of TTR aggregation in a biologically relevant environment, opening new avenues of investigation into the molecular mechanisms of LA.
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Affiliation(s)
- Estefania P C Azevedo
- Instituto de Bioquímica Médica, Programa de Biologia Estrutural, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-590 Brazil
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19
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Patel J, Landers K, Li H, Mortimer R, Richard K. Oxygen concentration regulates expression and uptake of transthyretin, a thyroxine binding protein, in JEG-3 choriocarcinoma cells. Placenta 2011; 32:128-33. [DOI: 10.1016/j.placenta.2010.11.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 11/18/2010] [Accepted: 11/23/2010] [Indexed: 01/11/2023]
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Abstract
The obesogen concept proposes that environmental contaminants may be contributing to the epidemic of obesity and its related pathology, metabolic disorder. The first references to such a notion appeared at the beginning of the current decade, with the hypothesis that the correlation between increasing incidence of obesity and enhanced industrial chemical production was not simply coincidental, but potentially causally related. The next event was the introduction of the term "obesogen" as representing an environmental pollutant that adversely affects various aspects of adipose tissue functions. More recently, the concept was extended to include substances that may modify metabolic balance at the central, hypothalamic level. The actions of two prime candidate obesogens, tributyltin (TBT) and tetrabromobisphenol A (TBBPA), acting at the central level are the main focus of this review. Having discussed the evidence for contaminant accumulation in the environment and in human tissues and the potential mechanisms of action, data are provided showing that these two widespread pollutants modify hypothalamic gene regulations. Our studies are based on maternal exposure and measurement of effects in the progeny, mainly based on in vivo gene reporter assays. Such models are obviously pertinent to testing current hypotheses that propose that early exposure might exert effects on later development and physiological functions. The potential molecular mechanisms involved are discussed, as are the broader physiological consequences of these hypothalamic dysregulations.
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Affiliation(s)
- Stéphanie Decherf
- CNRS UMR 7221 «Evolution of Endocrine Regulations», Department Regulations, Development and Molecular Diversity, Muséum National d'Histoire Naturelle, Paris, France.
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21
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Kodavanti PRS, Curras-Collazo MC. Neuroendocrine actions of organohalogens: thyroid hormones, arginine vasopressin, and neuroplasticity. Front Neuroendocrinol 2010; 31:479-96. [PMID: 20609372 DOI: 10.1016/j.yfrne.2010.06.005] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/22/2010] [Accepted: 06/25/2010] [Indexed: 02/08/2023]
Abstract
Organohalogen compounds are global environmental pollutants. They are highly persistent, bioaccumulative, and cause adverse effects in humans and wildlife. Because of the widespread use of these organohalogens in household items and consumer products, indoor contamination may be a significant source of human exposure, especially for children. One significant concern with regard to health effects associated with exposure to organohalogens is endocrine disruption. This review focuses on PCBs and PBDEs as old and new organohalogens, respectively, and their effects on two neuroendocrine systems; thyroid hormones and the arginine vasopressin system (AVP). Regarding neuroendocrine effects of organohalogens, there is considerable information on the thyroid system as a target and evidence is now accumulating that the AVP system and associated functions are also susceptible to disruption. AVP-mediated functions such as osmoregulation, cardiovascular function as well as social behavior, sexual function and learning/memory are discussed. For both thyroid and AVP systems, the timing of exposure seems to play a major role in the outcome of adverse effects. The mechanism of organohalogen action is well understood for the thyroid system. In comparison, this aspect is understudied in the AVP system but some similarities in neural processes, shown to be targeted by these pollutants, serve as promising possibilities for study. One challenge in understanding modes of action within neuroendocrine systems is their complexity stemming, in part, from interdependent levels of organization. Further, because of the interplay between neuroendocrine and neural functions and behavior, further investigation into organohalogen-mediated effects is warranted and may yield insights with wider scope. Indeed, the current literature provides scattered evidence regarding the role of organohalogen-induced neuroendocrine disruption in the neuroplasticity related to both learning functions and brain structure but future studies are needed to establish the role of endocrine disruption in nervous system function and development.
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Affiliation(s)
- Prasada Rao S Kodavanti
- Neurotoxicology Branch, Toxicity Assessment Division, B 105-06, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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22
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Wan Y, Choi K, Kim S, Ji K, Chang H, Wiseman S, Jones PD, Khim JS, Park S, Park J, Lam MHW, Giesy JP. Hydroxylated polybrominated diphenyl ethers and bisphenol A in pregnant women and their matching fetuses: placental transfer and potential risks. Environ Sci Technol 2010; 44:5233-9. [PMID: 20509646 DOI: 10.1021/es1002764] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are suspected endocrine disruptors, which can pass through the mammalian placenta and accumulate in the human maternal-fetal-placental unit. However, little is known about mechanisms of placental transfer and the associated risk(s). Ten OH-PBDE congeners, bisphenol A (BPA), total 17beta-estradiol (E2), and total thyroxine (T4) were quantified in blood serum from 26 pregnant women and 28 matching fetuses, including three pairs of twins from South Korea. Only 6-OH-BDE-47, a naturally occurring OH-PBDE, was detected at relatively great concentrations (maternal serum: 17.5 +/- 26.3 pg/g ww, fetal cord blood serum: 30.2 +/- 27.1 pg/g ww), which suggests that exposure was related to diets among Korean women. Concentrations of 6-OH-BDE-47 in maternal and cord serum were positively correlated, with concentrations being significantly greater in cord blood serum. The placental transfer ratio between fetal and maternal blood serum for 6-OH-BDE-47 (F/M ratio: 1.4 +/- 1.1) was different than the observed placental transfer ratio of BPA and previously reported values for hydroxylated polychlorinated biphenyls (OH-PCBs). This result is possibly due to large affinities to T4 transport proteins. Lesser concentrations of E2 and T4 were detected in cord blood serum (E2: 4.7 +/- 2.2 ng/mL, T4: 8.5 +/- 1.7 microg/dL) compared to maternal blood serum (E2: 8.0 +/- 3.0 ng/mL, T4: 9.7 +/- 1.8 microg/dL). A major effect of OH-PBDE exposure might be a decrease in serum T4 concentrations. Potential risks associated with disruption of T4 transport to the developing fetus such as negative consequences for fetal neurological development should be considered in further studies.
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Affiliation(s)
- Yi Wan
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada
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23
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Quintela T, Gonçalves I, Martinho A, Alves CH, Saraiva MJ, Rocha P, Santos CRA. Progesterone enhances transthyretin expression in the rat choroid plexus in vitro and in vivo via progesterone receptor. J Mol Neurosci 2010; 44:152-8. [PMID: 20535645 DOI: 10.1007/s12031-010-9398-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 05/23/2010] [Indexed: 10/19/2022]
Abstract
Depletion of ovarian hormones 17β-estradiol (E2) and progesterone (P) after menopause may contribute to the decline in cognitive performance and increases the risk of Alzheimer's disease (AD) in women, striking the importance of understanding the regulation of pivotal proteins involved in AD pathogenesis by ovarian hormones. Transthyretin (TTR) is now recognized as one of such proteins due to its ability to sequester and degrade amyloid β (Aβ) into less harmful peptides and preventing their aggregation. We have previously demonstrated that E2 enhances TTR expression. In this study, we investigate the effects of P on TTR expression in primary cultures of rat choroid plexus epithelial cells and in adult ovariectomized female rats. The results obtained demonstrate that, in vitro and in vivo, TTR is up-regulated by P. In addition, the mechanism underlying the response of TTR to P was investigated, and we provide evidence that this response is achieved through a progesterone receptor-mediated mechanism. Our results reinforce the importance of ovarian hormones on the regulation of TTR, which may reflect on the processing of Aβ peptides and consequently on AD onset and progression.
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Affiliation(s)
- Telma Quintela
- Health Sciences Research Centre-CICS, University of Beira Interior, Av. Infante D. Henrique, Covilhã, Portugal
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24
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Gutleb AC, Cenijn P, Velzen MV, Lie E, Ropstad E, Skaare JU, Malmberg T, Bergman A, Gabrielsen GW, Legler J. In vitro assay shows that PCB metabolites completely saturate thyroid hormone transport capacity in blood of wild polar bears (Ursus maritimus). Environ Sci Technol 2010; 44:3149-54. [PMID: 20345174 DOI: 10.1021/es903029j] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Persistent chemicals accumulate in the arctic environment due to their chemical reactivity and physicochemical properties and polychlorinated biphenyls (PCBs) are the most concentrated pollutant class in polar bears (Ursus maritimus). Metabolism of PCB and polybrominated biphenyl ether (PBDE) flame-retardants alter their toxicological properties and these metabolites are known to interfere with the binding of thyroid hormone (TH) to transthyretin (TTR) in rodents and humans. In polar bear plasma samples no binding of [125I]-T(4) to TTR was observed after incubation and PAGE separation. Incubation of the plasma samples with [14C]-4-OH-CB107, a compound with a higher binding affinity to TTR than the endogenous ligand T(4) resulted in competitive binding as proven by the appearance of a radio labeled TTR peak in the gel. Plasma incubation with T(4) up to 1 mM, a concentration that is not physiologically relevant anymore did not result in any visible competition. These results give evidence that the binding sites on TTR for T(4) in wild living polar bears are completely saturated. Such saturation of binding sites can explain observed lowered levels of THs and could lead to contaminant transport into the developing fetus.
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Affiliation(s)
- Arno C Gutleb
- Department Environment and Agro-biotechnologies, Centre de Recherche Public-Gabriel Lippmann, 41 Rue du Brill, L-4422 Belvaux, Grand-duchy of Luxembourg.
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25
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Abstract
Transthyretin (TTR) is the protein transporter of thyroxine and retinol. Several TTR mutations are associated with familial amyloid polyneuropathy, a neurodegenerative disorder characterized by extracellular deposition of TTR aggregates and fibrils in the peripheral nervous system. Several reports suggest new TTR functions in the nervous system particularly in nerve regeneration and in neuroprotection in Alzheimer’s disease. The fact that TTR increases axonal growth during peripheral nervous system, regeneration and allows an appropriate retrograde transport may represent the missing link explaining the preferential deposition of mutated TTR in the peripheral nervous system of familial amyloid polyneuropathy patients. This paper discusses the details explaining the role of TTR during nerve regeneration.
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Affiliation(s)
- Fernando M Mar
- Instituto de Biologia Molecular & Celular (IBMC), Nerve Regeneration Group, 4150–4180 Porto, Portugal and Instituto de Ciências Biomédicas Abel Salazar (IBMC), Universidade do Porto, 4099–5003 Porto, Portugal
| | - Filipa Franquinho
- Instituto Politécnico de Saúde-Norte/CESPU; Gandra PRD, Portugal and Instituto de Biologia Molecular & Celular (IBMC), Nerve Regeneration Group, 4150–4180 Porto, Portugal
| | - Carolina E Fleming
- Instituto de Ciências Biomédicas Abel Salazar (IBMC), Universidade do Porto, 4099–5003 Porto, Portugal
| | - Mónica M Sousa
- Instituto de Biologia Molecular & Celular (IBMC), Nerve Regeneration Group, 4150–4180 Porto, Portugal
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26
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Park HY, Park JS, Sovcikova E, Kocan A, Linderholm L, Bergman A, Trnovec T, Hertz-Picciotto I. Exposure to hydroxylated polychlorinated biphenyls (OH-PCBs) in the prenatal period and subsequent neurodevelopment in eastern Slovakia. Environ Health Perspect 2009; 117:1600-6. [PMID: 20019912 PMCID: PMC2790516 DOI: 10.1289/ehp.0900611] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [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: 01/23/2009] [Accepted: 05/20/2009] [Indexed: 05/17/2023]
Abstract
BACKGROUND Hydroxylated polychlorinated biphenyls (OH-PCBs), unlike PCBs, are in general readily excreted yet are still detected in humans and animals. Active transport of OH-PCBs across the placenta and hydroxylation of PCBs by the fetus suggest the potential for greater impact on the fetus compared with the parent PCB compounds, but little is known about their health effects, particularly in humans. OBJECTIVES The objective of this study was to evaluate the associations between prenatal OH-PCB exposure and neurodevelopment in children at 16 months of age in eastern Slovakia. METHODS A birth cohort (n = 1,134) was enrolled during 2002-2004. We analyzed six OH-PCB metabolites (4-OH-CB-107, 3-OH-CB-153, 4-OH-CB-146, 3'-OH-CB-138, 4-OH-CB-187, and 4'-OH-CB-172) in a subset of the cohort. The Bayley Scales of Infant Development were administered to the children at the 16-month follow-up visit. We developed multiple linear regression models predicting standardized scores for the Mental Development Index (MDI) and Psychomotor Development Index (PDI) from maternal (n = 147) and cord (n = 80) serum OH-PCB concentrations, adjusting for sex of child, district, HOME (Home Observation for Measurement of the Environment) score, and maternal score on Raven's Progressive Matrices. RESULTS Cord 4-OH-CB-107 was significantly associated with lower MDI (beta = -2.27; p = 0.01) and PDI (beta = -4.50; p = 0.004). Also, maternal 4-OH-CB-107 was significantly associated with lower MDI (beta = -1.76; p = 0.03) but not PDI. No other OH-PCB metabolites were associated with decreased PDI or MDI. CONCLUSIONS Our findings showed a significant association of 4-OH-CB-107 with decreased MDI, which can possibly be mediated by endocrine disruption, altered neurotransmitter functions, or reduced thyroid hormone concentrations in brain.
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Affiliation(s)
- Hye-Youn Park
- Division of Epidemiology, Department of Public Health Sciences, School of Medicine, University of California–Davis, Davis, California, USA
| | - June-Soo Park
- Division of Epidemiology, Department of Public Health Sciences, School of Medicine, University of California–Davis, Davis, California, USA
- California Department of Toxic Substances Control, California Environmental Protection Agency, Berkeley, California, USA
| | - Eva Sovcikova
- Department of Toxic Organic Pollutants, Slovak Medical University, Bratislava, Slovakia
| | - Anton Kocan
- Department of Toxic Organic Pollutants, Slovak Medical University, Bratislava, Slovakia
| | - Linda Linderholm
- Department of Environmental Chemistry, Stockholm University, Stockholm, Sweden
| | - Ake Bergman
- Department of Environmental Chemistry, Stockholm University, Stockholm, Sweden
| | - Tomas Trnovec
- Department of Toxic Organic Pollutants, Slovak Medical University, Bratislava, Slovakia
| | - Irva Hertz-Picciotto
- Division of Epidemiology, Department of Public Health Sciences, School of Medicine, University of California–Davis, Davis, California, USA
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Dallaire R, Dewailly É, Pereg D, Dery S, Ayotte P. Thyroid function and plasma concentrations of polyhalogenated compounds in Inuit adults. Environ Health Perspect 2009; 117:1380-6. [PMID: 19750101 PMCID: PMC2737013 DOI: 10.1289/ehp.0900633] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [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: 01/30/2009] [Accepted: 05/12/2009] [Indexed: 05/02/2023]
Abstract
BACKGROUND Several ubiquitous polyhalogenated compounds (PHCs) have been shown to alter thyroid function in animal and in vitro studies. So far, epidemiologic studies have focused on the potential effect of a small number of them, namely, polychlorinated biphenyls (PCBs) and some organochlorines (OCs), without paying attention to other important PHCs. OBJECTIVES We investigated the relationship between exposure to several PHCs and thyroid hormone homeostasis in Inuit adults from Nunavik. METHODS We measured thyroid parameters [thyroid-stimulating-hormone (TSH), free thyroxine (fT(4)), total triiodothyronine (tT(3)), and thyroxine-binding globulin (TBG)] and concentrations of 41 contaminants, including PCBs and their metabolites, organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), perfluorooctanesulfonate (PFOS), and a measure of dioxin-like compounds, detected in plasma samples from Inuit adults (n = 623). RESULTS We found negative associations between tT(3) concentrations and levels of 14 PCBs, 7 hydroxylated PCBs (HO-PCBs), all methylsulfonyl metabolites of PCBs (MeSO(2)-PCBs), and 2 OCPs. Moreover, we found negative associations between fT(4) levels and hexachlorobenzene concentrations. TBG concentrations were inversely related to 8 PCBs, 5 HO-PCBs, and 3 OCPs. Exposure to BDE-47 was positively related to tT (3), whereas PFOS concentrations were negatively associated with TSH, tT(3,) and TBG and positively with fT(4) concentrations. CONCLUSION Exposure to several PHCs was associated with modifications of the thyroid parameters in adult Inuit, mainly by reducing tT(3) and TBG circulating concentrations. The effects of PFOS and BDE-47 on thyroid homeostasis require further investigation because other human populations display similar or higher concentrations of these chemicals.
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Affiliation(s)
- Renée Dallaire
- Public Health Research Unit, Centre hospitalier universitaire de Québec-CHUL, Québec, Canada
| | - Éric Dewailly
- Public Health Research Unit, Centre hospitalier universitaire de Québec-CHUL, Québec, Canada
| | - Daria Pereg
- Public Health Research Unit, Centre hospitalier universitaire de Québec-CHUL, Québec, Canada
| | - Serge Dery
- Nunavik Regional Board of Health and Social Services, Kuujjuaq, Canada
| | - Pierre Ayotte
- Public Health Research Unit, Centre hospitalier universitaire de Québec-CHUL, Québec, Canada
- Address correspondence to P. Ayotte, Unité de recher-che en santé publique, Centre hospitalier universitaire de Québec-CHUL, 2875 boulevard Laurier Édifice Delta, 2 bureau 600, Québec, G1V 2M2 Canada. Telephone: (418) 656-4141 ext. 46519. Fax: (418) 654-2726. E-mail:
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Dallaire R, Muckle G, Dewailly É, Jacobson SW, Jacobson JL, Sandanger TM, Sandau CD, Ayotte P. Thyroid hormone levels of pregnant inuit women and their infants exposed to environmental contaminants. Environ Health Perspect 2009; 117:1014-20. [PMID: 19590699 PMCID: PMC2702396 DOI: 10.1289/ehp.0800219] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [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: 09/24/2008] [Accepted: 01/28/2009] [Indexed: 05/17/2023]
Abstract
BACKGROUND An increasing number of studies have shown that several ubiquitous environmental contaminants possess thyroid hormone-disrupting capacities. Prenatal exposure to some of them, such as polychlorinated biphenyls (PCBs), has also been associated with adverse neurodevelopmental effects in infants. OBJECTIVES In this study we examined the relationship between exposure to potential thyroid hormone-disrupting toxicants and thyroid hormone status in pregnant Inuit women from Nunavik and their infants within the first year of life. METHODS We measured thyroid hormone parameters [thyroid stimulating hormone (TSH), free thyroxine (fT(4)), total triiodothyronine (T(3)), thyroxine-binding globulin (TBG)] and concentrations of several contaminants [PCB-153, hydroxylated metabolites of PCBs (HO-PCBs), pentachlorophenol (PCP) and hexachlorobenzene (HCB)] in maternal plasma at delivery (n = 120), in umbilical cord plasma (n = 95), and in infant plasma at 7 months postpartum (n = 130). RESULTS In pregnant women, we found a positive association between HO-PCBs and T(3) concentrations (beta = 0.57, p = 0.02). In umbilical cord blood, PCB-153 concentrations were negatively associated with TBG levels (beta = -0.26, p = 0.01). In a subsample analysis, a negative relationship was also found between maternal PCP levels and cord fT(4) concentrations in neonates (beta = -0.59, p = 0.02). No association was observed between contaminants and thyroid hormones at 7 months of age. CONCLUSION Overall, there is little evidence that the environmental contaminants analyzed in this study affect thyroid hormone status in Inuit mothers and their infants. The possibility that PCP may decrease thyroxine levels in neonates requires further investigation.
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Affiliation(s)
- Renée Dallaire
- Public Health Research Unit, Centre Hospitalier Universitaire de Québec-CHUL, Québec City, Québec, Canada
- Department of Social and Preventive Medicine, Laval University, Québec City, Québec, Canada
| | - Gina Muckle
- Public Health Research Unit, Centre Hospitalier Universitaire de Québec-CHUL, Québec City, Québec, Canada
- School of Psychology, Laval University, Québec City, Québec, Canada
| | - Éric Dewailly
- Public Health Research Unit, Centre Hospitalier Universitaire de Québec-CHUL, Québec City, Québec, Canada
- Department of Social and Preventive Medicine, Laval University, Québec City, Québec, Canada
| | - Sandra W. Jacobson
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Joseph L. Jacobson
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA
- Department of Obstetrics and Gynecology, and Psychology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Torkjel M. Sandanger
- Norwegian Institute for Air Research, The Polar Environmental Centre, Tromsø, Norway
| | | | - Pierre Ayotte
- Public Health Research Unit, Centre Hospitalier Universitaire de Québec-CHUL, Québec City, Québec, Canada
- Department of Social and Preventive Medicine, Laval University, Québec City, Québec, Canada
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Palhano FL, Leme LP, Busnardo RG, Foguel D. Trapping the monomer of a non-amyloidogenic variant of transthyretin: exploring its possible use as a therapeutic strategy against transthyretin amyloidogenic diseases. J Biol Chem 2008; 284:1443-53. [PMID: 18984591 DOI: 10.1074/jbc.m807100200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transthyretin (TTR) is a 127-residue homotetrameric beta-sheet-rich protein that transports thyroxine in the blood and cerebrospinal fluid. The deposition of fibrils and amorphous aggregates of TTR in patients' tissues is a hallmark of TTR amyloid disease. Familial amyloidotic polyneuropathy is a hereditary form of TTR amyloidosis that is associated with one among 80 different variants of TTR. The most aggressive variants of TTR are V30M, L55P, and A25T, and the propensity to undergo aggregation seems to be linked to tetramer stability. T119M is a very stable, non-amyloidogenic variant of TTR. Here we show that the combination of high hydrostatic pressure with subdenaturing concentrations of urea (4 m) at 1 degrees C irreversibly dissociates T119M into monomers in less than 30 min in a concentration-dependent fashion. After pressure and urea removal, long lived monomers are the only species present in solution. We took advantage of the slow reassociation kinetics of these monomers into tetramers to produce heterotetramers by mixing the T119M monomers with the tetramers of the aggressive mutants of TTR. Our data show that T119M monomers can be successfully incorporated into all of these tetramers even when the exchange is performed in a more physiological environment such as human plasma; these monomers render the resultant heterotetramers less amyloidogenic. The data presented here are relevant for the understanding of T119M folding and association reactions and provide a protocol for producing T119M monomers that function as inhibitors of TTR aggregation when incorporated in to tetramers. This protocol may provide a new strategy for treating TTR diseases for which there is no therapy available other than liver transplantation.
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Affiliation(s)
- Fernando L Palhano
- Instituto de Bioquímica Médica, Programa de Biologia Estrutural, and Instituto Milênio de Biologia Estrutural e Biotecnologia Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-590, Brazil
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Abstract
Brominated flame retardants (BFR) are endocrine disrupters in experimental systems, both in vitro and in vivo. Although BFR effects on thyroid hormones are well confirmed, studies of effects on oestrogen/androgen systems are fewer but today growing in numbers. The effects of BFR on other hormone systems are still unknown. Hormonal effect levels in animals start from ca 1 mg/kg b.w., but there are exceptions: effects on spermatogenesis, suggesting hormonal causes, have been observed at a low dose (60 microg/kg b.w.) of a polybrominated diphenyl ether (PBDE) congener, BDE-99. It could be concluded that hormonal effects are of importance in risk assessment, and in some cases where effects are seen at low levels safety margins may be insufficient. One additional uncertainty is the lack of reliable human data that could be used to support animal BFR observations. In spite of the recent regulation of PBDE production, levels of both PBDE and of other BFR groups are still present in environmental samples. Thus, we have to deal with the possible effects of human BFR exposure for times to come. In order to reduce BFR exposure, the routes of exposure should be carefully examined and ways to reduce levels in major exposure routes considered.
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Chang KH, Lyu RK, Tseng MY, Ro LS, Wu YR, Chang HS, Hsu WC, Kuo HC, Huang CC, Chu CC, Hsieh SY, Chen CM. Elevated haptoglobin level of cerebrospinal fluid in Guillain-Barré syndrome revealed by proteomics analysis. Proteomics Clin Appl 2007; 1:467-75. [PMID: 21136698 DOI: 10.1002/prca.200600949] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Indexed: 11/06/2022]
Abstract
Guillain-Barré Syndrome (GBS) is a rare autoimmune inflammatory polyneuropathy with a high risk of respiratory failure and unclear pathogenesis. Currently, there are no valid biomarkers for diagnosis of GBS. We used 2-DE and MS to analyze the protein profiles of five pairs of cerebrospinal fluid (CSF) samples of the GBS patients and the patient controls. Three proteins (orosomucoid, haptoglobin and apolipoprotein A-IV) were up-regulated, and two proteins (prostaglandin D2 synthase and transthyretin) were down-regulated in the CSF of the GBS patients. The CSF haptoglobin level, quantified by enzyme-linked immunosorbent assay, was significantly higher in the GBS patients (12.44 ± 2.70 μg/mL) compared to the chronic inflammatory demyelinating polyradiculoneuropathy (2.82 ± 0.83 μg/mL), viral meningitis (3.57 ± 0.97 μg/mL) and control patients (1.44 ± 0.35 μg/mL, p<0.05). This study indicated that protein profile analysis using a combination of 2-DE and MS provides an effective strategy for elucidating the pathogenesis and identifying potential CSF biomarkers for GBS. The raised intrathecal synthesis of haptoglobin specifically only in GBS patients, but not in patients with other neurological diseases examined, provides evidence of central nervous system involvement in GBS, and may be used as a potential diagnostic marker for GBS.
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Affiliation(s)
- Kuo-Hsuan Chang
- Department of Neurology, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taipei, Taiwan
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Abstract
Spreading depression (SD) is a slowly propagating wave of neuronal depolarization altering ion homeostasis, blood flow and energy metabolism without causing irreversible damage of the tissue. As SD has been implicated in several neurological diseases including migraine and stroke, understanding these disorders requires systematic knowledge of the processes modified by SD. Thus, we induced repetitive SD in the rat cerebral cortex by topical application of 3 m KCl for approximately 2 h and evaluated the kinetics of SD-induced changes in cortical gene expression for up to 30 days using Affymetrix RAE230A arrays. The temporal profile showed a rapid expression of immediate early genes, genes associated with inflammation, metabolism, stress and DNA repair, ion transport, and genes that play a role in growth/differentiation. Stress-response genes could still be detected after 24 h. At this time, induced genes were mainly related to the cell membrane and adhesion, or to the cytoskeleton. A subset of genes was still affected even 30 days after SD. Real-time polymerase chain reactions and immunohistochemistry confirmed the microarray results for several of the transcripts. Our findings demonstrate a temporal pattern of gene expression which might promote tissue remodeling and cortical plasticity, and might probably account for the mediation of neuronal tolerance towards subsequent ischemia.
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Affiliation(s)
- Anja Urbach
- Department of Neurology, Friedrich-Schiller-University, Erlanger Allee 101, 07747 Jena, Germany.
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Abstract
Persistent organic pollutants (POPs) are long-lived toxic organic compounds and are of major concern for human and ecosystem health. Although the use of most POPs is banned in most countries, some organochlorine pesticides are still being used in several parts of the world. Although environmental levels of some POPs such as polychlorinated biphenyls (PCBs) have declined, newly emerging POPs such as polybrominated diphenyl ethers (PBDEs) have been increasing considerably. Exposure to POPs has been associated with a wide spectrum of effects including reproductive, developmental, immunologic, carcinogenic, and neurotoxic effects. It is of particular concern that neurotoxic effects of some POPs have been observed in humans at low environmental concentrations. This review focuses on PCBs as a representative chemical class of POPs and discusses the possible mode(s) of action for the neurotoxic effects with emphasis on comparing dose-response and structure-activity relationships (SAR) with other structurally related chemicals. There is sufficient epidemiological and experimental evidence showing that PCB exposure is associated with motor and cognitive deficits in humans and animal models. Although several potential mode(s) of actions were postulated for PCB-induced neurotoxic effects, changes in neurotransmitter systems, altered intracellular signalling processes, and thyroid hormone imbalance are predominant ones. These three potential mechanisms are discussed in detail in vitro and in vivo. In addition, SAR was conducted on other structurally similar chemicals to see if they have a common mode(s) of action. Relative potency factors for several of these POPs were calculated based on their effects on intracellular signalling processes. This is a comprehensive review comparing molecular effects at the cellular level to the neurotoxic effects seen in the whole animal for environmentally relevant POPs.
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Affiliation(s)
- Prasada Rao S Kodavanti
- Cellular and Molecular Toxicology Branch, Neurotoxicology Division, NHEERL/ORD, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Lei M, Yang M, Huo S. Intrinsic versus mutation dependent instability/flexibility: a comparative analysis of the structure and dynamics of wild-type transthyretin and its pathogenic variants. J Struct Biol 2005; 148:153-68. [PMID: 15477096 DOI: 10.1016/j.jsb.2004.06.007] [Citation(s) in RCA: 15] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Indexed: 11/25/2022]
Abstract
Transthyretin (TTR) is one of the about 20 known human proteins associated with amyloidosis which is characterized by the accumulation of amyloid fibrils in tissues or extracellular matrix surrounding vital organs. Unlike Alzheimer's fibrils that comprise a fragment of a large precursor protein, TTR amyloid fibrils are composed of both full-length protein and fragments of the molecule. The native state of TTR is a homotetramer with eight beta-strands organized into a beta-sandwich in each monomer. To elucidate the structural reorganization mechanisms preceding amyloid formation, it is important to characterize the dynamic features of the wild-type native state as well as to reveal the influence of disease-associated mutations on the structure and dynamics. Molecular dynamics (MD) simulations complement X-ray crystallography and D-H exchange to capture the intrinsically unstable/flexible sites of the wild-type as well as the mutation dependent unstable sites of the pathogenic variants. Our results of MD simulations have shown that the Leu55-->Pro (L55P) mutation occurs in an intrinsically unstable site, leading to substantial local and global structural changes. This observation supports the early speculation that the C-strand-loop-D-strand rearrangement leads to the formation of amyloidogenic intermediates. In addition to the D strand, the alpha-helical region and the strands at the monomer-monomer interface are also intrinsically unstable. The central channel of L55P-TTR undergoes opening and closing fluctuations, which may provide an explanation for the fact that while the mutation is far from the channel, the mutant shows a substantial low binding affinity of thyroxine.
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Affiliation(s)
- Ming Lei
- Gustaf H. Carlson school of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, MA 01610, USA
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35
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Abstract
The action of thyroid hormones (thyroxine, T4; triiodothyronine, T3) on brain development and function is gaining renewed interest. It has been known for many years that thyroid hormones are very important in mammalian brain maturation, influencing many aspects related to neural cell migration, differentiation, and signaling. In the last 10 years, genes regulated by thyroid hormones have been identified in the rodent brain, and understanding of the role of thyroid hormone nuclear receptors has been facilitated with the analysis of the phenotype of mutant mice for the different receptor isoforms. The general picture that emerges is that T4 and T3 may enter the brain through specific transporters. T4 is converted to the active hormone, T3, in glial cells, astrocytes, and tanycytes, although the main target cells are neurons and maturing oligodendrocytes. T3, acting through the nuclear receptors, controls the expression of genes involved in myelination, cell differentiation, migration, and signaling. In addition to transducing the T3 signal, the nuclear receptors also have activity in the unliganded state (i.e., as aporeceptors), mainly as repressors of transcription. The physiological meaning of aporreceptor action is not known, but they may play a role in the genesis of the hypothyroid phenotype. Among the questions that remain to be explored in more detail is the role of thyroid hormones and the T3 receptors, both liganded and unliganded, in the fetal brain, especially before onset of fetal thyroid gland function. These questions are relevant for human health and the management of thyroid diseases during pregnancy.
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Affiliation(s)
- Juan Bernal
- Instituto de Investigaciones Biomedicas Alberto Sols, Consejo Superior de Investigaciones Cientificas and Universidad Autonoma de Madrid, 28029 Madrid, Spain
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Sousa JC, Grandela C, Fernández-Ruiz J, de Miguel R, de Sousa L, Magalhães AI, Saraiva MJ, Sousa N, Palha JA. Transthyretin is involved in depression-like behaviour and exploratory activity. J Neurochem 2004; 88:1052-8. [PMID: 15009661 DOI: 10.1046/j.1471-4159.2003.02309.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transthyretin (TTR), the major transporter of thyroid hormones and vitamin A in cerebrospinal fluid (CSF), binds the Alzheimer beta-peptide and thus might confer protection against neurodegeneration. In addition, altered TTR levels have been described in the CSF of patients with psychiatric disorders, yet its function in the CNS is far from understood. To determine the role of TTR in behaviour we evaluated the performance of TTR-null mice in standardized tasks described to assess depression, exploratory activity and anxiety. We show that the absence of TTR is associated with increased exploratory activity and reduced signs of depressive-like behaviour. In order to investigate the mechanism underlying these alterations, we measured the levels of catecholamines. We found that the levels of noradrenaline were significantly increased in the limbic forebrain of TTR-null mice. This report represents the first clear indication that TTR plays a role in behaviour, probably by modulation of the noradrenergic system.
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Abstract
Animal studies show that exposure to polychlorinated biphenyls (PCBs) or other persistent organochlorine compounds can disrupt thyroid hormone homeostasis. In some reports dietary exposures to PCBs have also been claimed to affect circulating levels of thyroid hormones and thyrotropin (TSH) in humans. The aim of the present study was to review available epidemiologic studies within this field. A total of 13 studies fulfilled the inclusion criteria for the review. The overall impression is a lack of consistency between studies of reported correlations, neither are there any obvious interstudy dose-response associations. Thus, it cannot presently be concluded that PCB exposure has been convincingly shown to affect thyroid hormone homeostasis in humans. On the other hand, available data do not exclude such associations. It is important to be aware of the intrinsic limitations of the cross-sectional epidemiologic studies used.
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Affiliation(s)
- Lars Hagmar
- Department of Occupational and Environmental Medicine, Lund University Hospital, Lund, Sweden.
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Yang M, Lei M, Huo S. Why is Leu55-->Pro55 transthyretin variant the most amyloidogenic: insights from molecular dynamics simulations of transthyretin monomers. Protein Sci 2003; 12:1222-31. [PMID: 12761393 PMCID: PMC2323890 DOI: 10.1110/ps.0239703] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [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: 10/27/2022]
Abstract
Transthyretin (TTR) is one of the known human amyloidogenic proteins. Its native state is a homotetramer with each monomer having a beta-sandwich structure. Strong experimental evidence suggests that TTR dissociates into monomeric intermediates and that the monomers subsequently self-assemble to form amyloid deposits and insoluble fibrils. However, details on the early steps along the pathway of TTR amyloid formation are unclear, although various experimental approaches with resolutions at the molecular or residue level have provided some clues. It is highly likely that the stability and flexibility of monomeric TTR play crucial roles in the early steps of amyloid formation; thereby, it is essential to characterize initial conformational changes of TTR monomers. In this article we probe the possibility that the differences in the monomeric forms of wild-type (WT) TTR and its variants are responsible for differential amyloidogenesis. We begin with the simulations of WT, Val30-->Met (V30M), and Leu55-->Pro (L55P) TTR monomers. Nanosecond time scale molecular dynamics simulations at 300 K were performed using AMBER. The results indicate that the L55P-TTR monomer undergoes substantial structural changes relative to fluctuations observed in the WT and V30M TTR monomers. The observation supports earlier speculation that the L55P mutation may lead to disruption of the beta-sheet structure through the disorder of the "edge strands" that might facilitate amyloidogenesis.
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Affiliation(s)
- Mingfeng Yang
- Gustaf H. Carlson School of Chemistry and Biochemistry, Worcester, Massachusetts 01610, USA
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Palha JA, Nissanov J, Fernandes R, Sousa JC, Bertrand L, Dratman MB, Morreale de Escobar G, Gottesman M, Saraiva MJ. Thyroid hormone distribution in the mouse brain: the role of transthyretin. Neuroscience 2002; 113:837-47. [PMID: 12182890 DOI: 10.1016/s0306-4522(02)00228-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [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: 11/17/2022]
Abstract
Transthyretin is the major thyroxine-binding protein in the plasma of rodents, and the main thyroxine-binding protein in the cerebrospinal fluid of both rodents and humans. The choroid plexus synthesizes transthyretin and secretes it to the cerebrospinal fluid. Although it was suggested that transthyretin might play an important role in mediating thyroxine transfer from the blood into the brain across the choroid plexus-cerebrospinal fluid barrier, newer findings question this hypothesis. Because thyroid hormone passage across brain barriers is a precondition for its action in the CNS, and because brain is an important target of thyroid hormone action, we investigated the role of transthyretin in mediating thyroid hormone access to and distribution within the brain in a transthyretin-null mouse model system. In this report we describe the results derived from use of film autoradiography, a technique that yields definitive morphological results. Film autoradiograms were prepared at 3 and 19 h after intravenous injection of either high specific activity [(125)I]thyroxine or [(125)I]triiodothyronine. Image analyses were designed to demonstrate regional changes in hormone distribution, and to highlight alterations in iodothyronine delivery from ventricles to brain parenchyma. We find no qualitative or quantitative differences in these parameters between the transthyretin-null and the wild-type mouse brain after either [(125)I]thyroxine or [(125)I]triiodothyronine administration. The data presented here now provide definitive evidence that, under standard laboratory conditions, transthyretin is not required for thyroid hormone access to or distribution within the mouse brain. This study also provides the first map of iodothyronine distribution in the brain of the mouse.
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Affiliation(s)
- J A Palha
- Unidade de Amilóide, Instituto de Biologia Molecular e Celular, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
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Abstract
Among the most critical actions of thyroid hormone in man and other mammals are those exerted on brain development. Severe hypothyroidism during the neonatal period leads to structural alterations, including hypomyelination and defects of cell migration and differentiation, with long-lasting, irreversible effects on behavior and performance. A complex regulatory mechanism operates in brain involving regulation of the concentration of the active hormone, T3, and the control of gene expression. Most brain T3 is formed locally from its precursor, T4, by the action of type II deiodinase which is expressed in glial cells, tanycytes, and astrocytes. Type III deiodinase (DIII) is also involved in the regulation of T3 concentrations, especially during the embryonic and early post-natal periods. DIII is expressed in neurons and degrades T4 and T3 to inactive metabolites. The action of T3 is mediated through nuclear receptors, which are expressed mainly in neurons. The receptors are ligand-modulated transcription factors, and a number of genes have been identified as regulated by thyroid hormone in brain. The regulated genes encode proteins of myelin, mitochondria, neurotrophins and their receptors, cytoskeleton, transcription factors, splicing regulators, cell matrix proteins, adhesion molecules, and proteins involved in intracellular signaling pathways. The role of thyroid hormone is to accelerate changes of gene expression that take place during development. Surprisingly, null-mutant mice for the T3 receptors show almost no signs of central nervous system involvement, in contrast with the severe effects of hypothyroidism. The resolution of this paradox is essential to understand the role of thyroid hormone and its receptors in brain development and function.
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Affiliation(s)
- J Bernal
- Instituto de Investigaciones Biomedicas Alberto Sols, Consejo Superior de Investigaciones Cientfficas, Universidad Autónoma de Madrid, Spain.
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Tenedieva VD, Potapov AA, Gaitur EI, Amcheslavski VG, Micrikova LV, Tenedieva ND, Voronov VG. Thyroid hormones in comatose patients with traumatic brain injury. Acta Neurochir Suppl 2001; 76:385-91. [PMID: 11450050 DOI: 10.1007/978-3-7091-6346-7_80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The objective was to study if thyroid hormones, cortisol, prolactin and brain injury marker levels were changed in traumatic brain injury (TBI) patients with changing levels of consciousness. We estimated the above named parameters in 32 patients (27 men and 5 women aged 11-55). Admission Glasgow Coma Score was < 8. Follow-up period--30 days. The length of coma was 3 to 25 days. There were significant decreases in TSH, TBG, FT3 and F_levels (p < 0.05, for each) and a T3 increase (as compared to very low preceding values) on day 1 before emergence from coma and considerable post-coma increase in TBG, FT3, TSH and F levels (p < 0.001 each) on days 1-3 in patients with diffuse axonal injury (DAI). In patients with contusions and epidural and subdural hematomas (CH) T3 and T4 levels continued to fall until 4-6 postcoma days. TSH values significantly increased up to average normal ranges (p < 0.05) on days "-" 2 and "-" 1 before emergence from coma and remained so. Significantly lower levels of TSH, F and PRL were found in patients with CH in the mostly remote period (on days "-" 12-"-" 8) before emergence from coma in comparison with DAI patients. In blood the following correlations of examined parameters were established: between NSE and T3 (r = -0.39), NSE and FT3 (r = -0.59), TNF alpha and TBG (r = -0.64), TNF alpha and T3 (r = -0.3) and S-100 and T3 (r = -0.3) (p < 0.05, for each). The results obtained confirmed a low T3 syndrome in comatose TBI patients. We demonstrated an objective and informative interdependence: the turning-point moment of the emergence from coma was accompanied by significant changes of examined hormone levels and brain injury marker levels. The results may serve as a base for recommending monitoring FT3 and T3 levels simultaneously with that of other injury markers and adequate T3 replacement therapy in the early posttraumatic period.
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Affiliation(s)
- V D Tenedieva
- Burdenko Neurosurgical Institute RAMS, Moscow, Russia
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Hennemann G, Docter R, Friesema EC, de Jong M, Krenning EP, Visser TJ. Plasma membrane transport of thyroid hormones and its role in thyroid hormone metabolism and bioavailability. Endocr Rev 2001; 22:451-76. [PMID: 11493579 DOI: 10.1210/edrv.22.4.0435] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.4] [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] [Indexed: 12/21/2022]
Abstract
Although it was originally believed that thyroid hormones enter target cells by passive diffusion, it is now clear that cellular uptake is effected by carrier-mediated processes. Two stereospecific binding sites for each T4 and T3 have been detected in cell membranes and on intact cells from humans and other species. The apparent Michaelis-Menten values of the high-affinity, low-capacity binding sites for T4 and T3 are in the nanomolar range, whereas the apparent Michaelis- Menten values of the low-affinity, high-capacity binding sites are usually in the lower micromolar range. Cellular uptake of T4 and T3 by the high-affinity sites is energy, temperature, and often Na+ dependent and represents the translocation of thyroid hormone over the plasma membrane. Uptake by the low-affinity sites is not dependent on energy, temperature, and Na+ and represents binding of thyroid hormone to proteins associated with the plasma membrane. In rat erythrocytes and hepatocytes, T3 plasma membrane carriers have been tentatively identified as proteins with apparent molecular masses of 52 and 55 kDa. In different cells, such as rat erythrocytes, pituitary cells, astrocytes, and mouse neuroblastoma cells, uptake of T4 and T3 appears to be mediated largely by system L or T amino acid transporters. Efflux of T3 from different cell types is saturable, but saturable efflux of T4 has not yet been demonstrated. Saturable uptake of T4 and T3 in the brain occurs both via the blood-brain barrier and the choroid plexus-cerebrospinal fluid barrier. Thyroid hormone uptake in the intact rat and human liver is ATP dependent and rate limiting for subsequent iodothyronine metabolism. In starvation and nonthyroidal illness in man, T4 uptake in the liver is decreased, resulting in lowered plasma T3 production. Inhibition of liver T4 uptake in these conditions is explained by liver ATP depletion and increased concentrations of circulating inhibitors, such as 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, indoxyl sulfate, nonesterified fatty acids, and bilirubin. Recently, several organic anion transporters and L type amino acid transporters have been shown to facilitate plasma membrane transport of thyroid hormone. Future research should be directed to elucidate which of these and possible other transporters are of physiological significance, and how they are regulated at the molecular level.
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Affiliation(s)
- G Hennemann
- Department of Nuclear Medicine, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands.
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Abstract
Transthyretin (TTR) belongs to a group of proteins, which includes thyroxine-binding globulin and albumin, that bind to and transport thyroid hormones in the blood. TTR is also indirectly implicated in the carriage of vitamin A through the mediation of retinol-binding protein (RBP). It was first identified in 1942 in human serum and cerebrospinal fluid and was formerly called prealbumin for its ability to migrate faster than serum albumin on electrophoresis of whole plasma. It is a single polypeptide chain of 127 amino acids (14,000 Da) and is present in the plasma as a tetramer of noncovalently bound monomers. The major sites of synthesis of TTR in eutherian mammals, marsupials, and birds are the liver and choroid plexus but in reptiles it is synthesised only in the choroid plexus. The observation that TTR is strongly expressed in the choroid plexus but not in the liver of the stumpy-tailed lizard and the strong conservation of expression in the choroid plexus from reptiles to mammals have been taken as evidence to suggest that extrahepatic synthesis of TTR evolved first. The identification and cloning of TTR from the liver of an amphibian, Rana catesbeiana, and a teleost fish, Sparus aurata, and its absence from the choroid plexus of both species suggest an alternative model for its evolution. Protein modelling studies are presented that demonstrate differences in the electrostatic characteristics of the molecule in human, rat, chicken, and fish, which may explain why, in contrast to TTR from human and rat, TTR from fish and birds preferentially binds triiodo-l-thyronine.
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Affiliation(s)
- D M Power
- Centro de Ciências de MAR (CCMAR), Universidade do Algarve, Campus de Gambelas, 8000 Faro, Portugal
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Sullivan GM, Hatterer JA, Herbert J, Chen X, Roose SP, Attia E, Mann JJ, Marangell LB, Goetz RR, Gorman JM. Low levels of transthyretin in the CSF of depressed patients. Am J Psychiatry 1999; 156:710-5. [PMID: 10327903 DOI: 10.1176/ajp.156.5.710] [Citation(s) in RCA: 21] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Transthyretin plays an important role in the transport and distribution of thyroid hormone in the central nervous system (CNS). This study replicated and extended to patients with nonrefractory depressive illness a pilot study indicating that patients with refractory major depression have significantly lower levels of CSF transthyretin than do healthy comparison subjects. METHOD Lumbar punctures were performed in drug-free subjects with DSM-III-R major depression (N = 18), DSM-III-R bipolar disorder, depressed phase (N = 1), and healthy comparison subjects (N = 24). CSF concentrations of transthyretin, determined by a quantitative dot-immunobinding assay, of the depressed patients and comparison subjects were compared by analysis of covariance (ANCOVA). The relationship between CSF transthyretin levels and Hamilton Depression Rating Scale scores was determined in a subset of the depressed patients. RESULTS CSF concentrations of transthyretin were significantly lower in the depressed patients than in the comparison subjects by ANCOVA. Within the depressed group there was no significant overall correlation between CSF transthyretin levels and Hamilton depression scale scores, but there was a significant inverse correlation in male depressed patients (N = 8) between CSF transthyretin concentrations and Hamilton depression scores. CONCLUSIONS Lower CSF transthyretin concentrations in depressed patients may reflect either a stable trait in this population or a state change secondary to depression or other factors. Lower CSF transthyretin concentrations may result in altered CNS thyroid hormone homeostasis. Such alteration could account for certain mood and neurovegetative symptoms of depression and might contribute to failure of standard antidepressant treatment.
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Affiliation(s)
- G M Sullivan
- Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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Zheng W, Blaner WS, Zhao Q. Inhibition by lead of production and secretion of transthyretin in the choroid plexus: its relation to thyroxine transport at blood-CSF barrier. Toxicol Appl Pharmacol 1999; 155:24-31. [PMID: 10036215 PMCID: PMC4126158 DOI: 10.1006/taap.1998.8611] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [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: 11/22/2022]
Abstract
Long-term, low-dose Pb exposure in rats is associated with a significant decrease in transthyretin (TTR) concentrations in the CSF. Since CSF TTR, a primary carrier of thyroxine in brain, is produced and secreted by the choroid plexus, in vitro studies were conducted to test whether Pb exposure interferes with TTR production and/or secretion by the choroid plexus, leading to an impaired thyroxine transport at the blood-CSF barrier. Newly synthesized TTR molecules in the cultured choroidal epithelial cells were pulse-labeled with [35S]methionine. [35S]TTR in the cell lysates and culture media was immunoprecipitated and separated by SDS-PAGE, and quantitated by autoradiography and liquid scintillation counting. Pb treatment did not significantly alter the protein concentrations in the culture, but inhibited the synthesis of total [35S]TTR (cells + media), particularly during the later chase phase. Two-way ANOVA of the chase phase revealed that Pb exposure (30 microM) significantly suppressed the rate of secretion of [35S]TTR compared to the controls (p < 0.05). Accordingly, Pb treatment caused a retention of [35S]TTR by the cells. In a two-chamber transport system with a monolayer of epithelial barrier, Pb exposure (30 microM) reduced the initial release rate constant (kr) of [125I]T4 from the cell monolayer to the culture media and impeded the transepithelial transport of [125I]T4 from the basal to apical side of epithelial cells by 27%. Taken together, these in vitro data suggest that sequestration of Pb in the choroid plexus hinders the production and secretion of TTR by this tissue. Consequently, this may alter the transport of thyroxine across this blood-CSF barrier.
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Affiliation(s)
- W Zheng
- School of Public Health, Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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Abstract
Synthetic chemicals are released into the environment by design (pesticides) or as a result of industrial activity. It is well known that natural environmental chemicals can cause goiter or thyroid imbalance. However, the effects of synthetic chemicals on thyroid function have received little attention, and there is much controversy over their potential clinical impact, because few studies have been conducted in humans. This article reviews the literature on possible thyroid disruption in wildlife, humans, and experimental animals and focuses on the most studied chemicals: the pesticides DDT, amitrole, and the thiocarbamate family, including ethylenethiourea, and the industrial chemicals polyhalogenated hydrocarbons, phenol derivatives, and phthalates. Wildlife observations in polluted areas clearly demonstrate a significant incidence of goiter and/or thyroid imbalance in several species. Experimental evidence in rodents, fish, and primates confirms the potentiality for thyroid disruption of several chemicals and illustrates the mechanisms involved. In adult humans, however, exposure to background levels of chemicals does not seem to have a significant negative effect on thyroid function, while exposure at higher levels, occupational or accidental, may produce mild thyroid changes. The impact of transgenerational, background exposure in utero on fetal neurodevelopment and later childhood cognitive function is now under scrutiny. There are several studies linking a lack of optimal neurological function in infants and children with high background levels of exposure to polychlorinated biphenyls (PCBs), dioxins, and/or co-contaminants, but it is unclear if the effects are caused by thyroid disruption in utero or direct neurotoxicity.
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Affiliation(s)
- F Brucker-Davis
- Wildlife and Contaminants Program, World Wildlife Fund, Washington, DC 20037, USA
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Reinert BD, Wilson FE. Effects of thyroxine (T4) or triiodothyronine (T3) replacement therapy on the programming of seasonal reproduction and postnuptial molt in thyroidectomized male American tree sparrows (Spizella arborea) exposed to long days. J Exp Zool 1997; 279:367-76. [PMID: 9360316 DOI: 10.1002/(sici)1097-010x(19971101)279:4<367::aid-jez6>3.0.co;2-m] [Citation(s) in RCA: 20] [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] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study tested the hypothesis that T3 (triiodothyronine) is the tissue-active "seasonality" hormone by determining whether T3 could mimic T4 (thyroxine) and program photostimulated thyroidectomized (THX) male American tree sparrows (Spizella arborea) for three components of seasonality (i.e., full-blown testicular growth, photorefractoriness, and postnuptial molt). Photosensitive males were radiothyroidectomized, transferred to long days 4 weeks later, and administered 14 daily injections (s.c.) of alkaline saline (V) containing 0.1, 1, or 10 micrograms T4 or T3. THX and thyroid-intact (THI) controls received only V. After 5 additional weeks on long days, all birds were tested for photosensitivity/photorefractoriness. Periodically during the experiment, primary flight feathers were scored for molt, and testis length was monitored by laparotomy. As an independent measure of reproductive (i.e., photosensitive vs. photorefractory) state, hypothalami collected at the end of the experiment were assayed for cGnRH-I (chicken gonadotropin-releasing hormone I) content. Like THI controls, THX males administered 1 or 10 micrograms T4 exhibited full-blown testicular growth and then regression, initiated molt, and had low hypothalamic cGnRH-I, indicating that photostimulated birds that received mid- or high-dose T4 replacement therapy had been programmed for all three components of seasonality. On the other hand, both THX controls and THX males administered low-dose (0.1 microgram) T3 replacement therapy exhibited only modest testicular growth, signifying that neither group had been programmed for any component of seasonality. By contrast, photostimulated THX males that received 0.1 microgram T4, or 1 or 10 micrograms T3, were programmed for testicular growth, but not for photorefractoriness or molt. Collectively, these results show that subcutaneously administered T3 mimicked T4 imperfectly and suggest either that T3 does not program photostimulated male tree sparrows for photorefractoriness and postnuptial molt, or that T3 does not cross the blood-brain barrier as efficiently as does T4.
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Affiliation(s)
- B D Reinert
- Division of Biology, Kansas State University, Manhattan 66506, USA.
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Abstract
Thyroxine, the most abundant thyroid hormone in blood, partitions into lipid membranes. In a network-like system, thyroxine-binding plasma proteins counteract this partitioning and establish intravascular, protein-bound thyroxine pools. These are far larger than the free thyroxine pools. In larger eutherians, proteins specifically binding thyroxine are albumin, transthyretin, and thyroxine-binding globulin. Some binding of thyroxine can also occur to lipoproteins. During evolution, transthyretin synthesis first appeared in the choroid plexus of the stem reptiles, about 300 million years ago. Transthretin synthesis in the liver evolved much later, independently, in birds, eutherians and some marsupial species. Analysis of 57 human transthyretin variants suggests that most mutations in transthyretin are not compatible with its normal metabolism and lead to its deposition as amyloid. Analysis of transthyretin or its gene in 20 different species shows that evolutionary changes of transthyretin predominantly occurred near the N-termini. A change in RNA splicing between exon 1 and exon 2 led to a decrease in hydrophobicity and length of the N-termini. It is proposed that the selection pressure producing these changes was the need for a more effective prevention of thyroxine partitioning into lipids. Lipid pools increased during evolution with the increases in relative sizes of brains and internal organs and changes in lipid composition of membranes in ectothermic and endothermic species.
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Affiliation(s)
- G Schreiber
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.
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Miroy GJ, Lai Z, Lashuel HA, Peterson SA, Strang C, Kelly JW. Inhibiting transthyretin amyloid fibril formation via protein stabilization. Proc Natl Acad Sci U S A 1996; 93:15051-6. [PMID: 8986762 PMCID: PMC26354 DOI: 10.1073/pnas.93.26.15051] [Citation(s) in RCA: 268] [Impact Index Per Article: 9.6] [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] [Received: 06/17/1996] [Accepted: 09/30/1996] [Indexed: 02/03/2023] Open
Abstract
Transthyretin (TTR) amyloid fibril formation is observed systemically in familial amyloid polyneuropathy and senile systemic amyloidosis and appears to be the causative agent in these diseases. Herein, we demonstrate conclusively that thyroxine (10.8 microM) inhibits TTR fibril formation efficiently in vitro and does so by stabilizing the tetramer against dissociation and the subsequent conformational changes required for amyloid fibril formation. In addition, the nonnative ligand 2,4,6-triiodophenol, which binds to TTR with slightly increased affinity also inhibits TTR fibril formation by this mechanism. Sedimentation velocity experiments were employed to show that TTR undergoes dissociation (linked to a conformational change) to form the monomeric amyloidogenic intermediate, which self-assembles into amyloid in the absence, but not in the presence of thyroxine. These results demonstrate the feasibility of using small molecules to stabilize the native fold of a potentially amyloidogenic human protein, thus preventing the conformational changes, which appear to be the common link in several human amyloid diseases. This strategy and the compounds resulting from further development should prove useful for critically evaluating the amyloid hypothesis--i.e., the putative cause-and-effect relationship between TTR amyloid deposition and the onset of familial amyloid polyneuropathy and senile systemic amyloidosis.
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Affiliation(s)
- G J Miroy
- Department of Chemistry, Texas A&M University, College Station 77843-3255, USA
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