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Roza M, Eriksson ANM, Svanholm S, Berg C, Karlsson O. Male-transmitted transgenerational effects of the herbicide linuron on DNA methylation profiles in Xenopus tropicalis brain and testis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 923:170949. [PMID: 38365020 DOI: 10.1016/j.scitotenv.2024.170949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 01/30/2024] [Accepted: 02/11/2024] [Indexed: 02/18/2024]
Abstract
The herbicide linuron can cause endocrine disrupting effects in Xenopus tropicalis frogs, including offspring that were never exposed to the contaminant. The mechanisms by which these effects are transmitted across generations need to be further investigated. Here, we examined transgenerational alterations of brain and testis DNA methylation profiles paternally inherited from grandfathers developmentally exposed to an environmentally relevant concentration of linuron. Reduced representation bisulfite sequencing (RRBS) revealed numerous differentially methylated regions (DMRs) in brain (3060 DMRs) and testis (2551 DMRs) of the adult male F2 generation. Key genes in the brain involved in somatotropic (igfbp4) and thyrotropic signaling (dio1 and tg) were differentially methylated and correlated with phenotypical alterations in body size, weight, hind limb length and plasma glucose levels, indicating that these methylation changes could be potential mediators of the transgenerational effects of linuron. Testis DMRs were found in genes essential for spermatogenesis, meiosis and germ cell development (piwil1, spo11 and tdrd9) and their methylation levels were correlated with the number of germ cells nests per seminiferous tubule, an endpoint of disrupted spermatogenesis. DMRs were also identified in several genes central for the machinery that regulates the epigenetic landscape including DNA methylation (dnmt3a and mbd2) and histone acetylation (hdac8, ep300, elp3, kat5 and kat14), which may at least partly drive the linuron-induced transgenerational effects. The results from this genome-wide DNA methylation profiling contribute to better understanding of potential transgenerational epigenetic inheritance mechanisms in amphibians.
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Affiliation(s)
- Mauricio Roza
- Science for Life Laboratory, Department of Environmental Science, Stockholm University, Stockholm, Sweden
| | | | - Sofie Svanholm
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | - Cecilia Berg
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | - Oskar Karlsson
- Science for Life Laboratory, Department of Environmental Science, Stockholm University, Stockholm, Sweden.
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2
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Du Pasquier D, Salinier B, Coady KK, Jones A, Körner O, LaRocca J, Lemkine G, Robin-Duchesne B, Weltje L, Wheeler JR, Lagadic L. How the Xenopus eleutheroembryonic thyroid assay compares to the amphibian metamorphosis assay for detecting thyroid active chemicals. Regul Toxicol Pharmacol 2024; 149:105619. [PMID: 38614220 DOI: 10.1016/j.yrtph.2024.105619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/05/2024] [Accepted: 04/03/2024] [Indexed: 04/15/2024]
Abstract
The Xenopus Eleutheroembryonic Thyroid Assay (XETA) was recently published as an OECD Test Guideline for detecting chemicals acting on the thyroid axis. However, the OECD validation did not cover all mechanisms that can potentially be detected by the XETA. This study was therefore initiated to investigate and consolidate the applicability domain of the XETA regarding the following mechanisms: thyroid hormone receptor (THR) agonism, sodium-iodide symporter (NIS) inhibition, thyroperoxidase (TPO) inhibition, deiodinase (DIO) inhibition, glucocorticoid receptor (GR) agonism, and uridine 5'-diphospho-glucuronosyltransferase (UDPGT) induction. In total, 22 chemicals identified as thyroid-active or -inactive in Amphibian Metamorphosis Assays (AMAs) were tested using the XETA OECD Test Guideline. The comparison showed that both assays are highly concordant in identifying chemicals with mechanisms of action related to THR agonism, DIO inhibition, and GR agonism. They also consistently identified the UDPGT inducers as thyroid inactive. NIS inhibition, investigated using sodium perchlorate, was not detected in the XETA. TPO inhibition requires further mechanistic investigations as the reference chemicals tested resulted in opposing response directions in the XETA and AMA. This study contributes refining the applicability domain of the XETA, thereby helping to clarify the conditions where it can be used as an ethical alternative to the AMA.
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Affiliation(s)
- David Du Pasquier
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | - Benoît Salinier
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | - Katherine K Coady
- Bayer Crop Science, Environmental Safety, 700 Chesterfield Parkway West, Chesterfield, MO, USA
| | - Alan Jones
- ADAMA US, Environmental Safety, 3120 Highwoods Blvd., Raleigh, NC, 27604, USA
| | - Oliver Körner
- ADAMA, Environmental Safety, Edmund-Rumpler-Strasse 6, 51149, Cologne, Germany
| | - Jessica LaRocca
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, IN, 46268, USA
| | - Gregory Lemkine
- Laboratoire WatchFrog, 1 Rue Pierre Fontaine, 91000, Évry-Courcouronnes, France
| | | | - Lennart Weltje
- BASF SE, Agricultural Solutions - Ecotoxicology, Speyerer Strasse 2, 67117, Limburgerhof, Germany
| | - James R Wheeler
- Corteva Agriscience, Zuid-Oostsingel 24D, 4611 BB, Bergen op Zoom, the Netherlands
| | - Laurent Lagadic
- Bayer AG R&D Crop Science, Alfred-Nobel-Strasse 50, 40789, Monheim am Rhein, Germany.
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Haigis AC, Vergauwen L, LaLone CA, Villeneuve DL, O'Brien JM, Knapen D. Cross-species applicability of an adverse outcome pathway network for thyroid hormone system disruption. Toxicol Sci 2023; 195:1-27. [PMID: 37405877 DOI: 10.1093/toxsci/kfad063] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023] Open
Abstract
Thyroid hormone system disrupting compounds are considered potential threats for human and environmental health. Multiple adverse outcome pathways (AOPs) for thyroid hormone system disruption (THSD) are being developed in different taxa. Combining these AOPs results in a cross-species AOP network for THSD which may provide an evidence-based foundation for extrapolating THSD data across vertebrate species and bridging the gap between human and environmental health. This review aimed to advance the description of the taxonomic domain of applicability (tDOA) in the network to improve its utility for cross-species extrapolation. We focused on the molecular initiating events (MIEs) and adverse outcomes (AOs) and evaluated both their plausible domain of applicability (taxa they are likely applicable to) and empirical domain of applicability (where evidence for applicability to various taxa exists) in a THSD context. The evaluation showed that all MIEs in the AOP network are applicable to mammals. With some exceptions, there was evidence of structural conservation across vertebrate taxa and especially for fish and amphibians, and to a lesser extent for birds, empirical evidence was found. Current evidence supports the applicability of impaired neurodevelopment, neurosensory development (eg, vision) and reproduction across vertebrate taxa. The results of this tDOA evaluation are summarized in a conceptual AOP network that helps prioritize (parts of) AOPs for a more detailed evaluation. In conclusion, this review advances the tDOA description of an existing THSD AOP network and serves as a catalog summarizing plausible and empirical evidence on which future cross-species AOP development and tDOA assessment could build.
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Affiliation(s)
- Ann-Cathrin Haigis
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Carlie A LaLone
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Daniel L Villeneuve
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Jason M O'Brien
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Carleton University, Ottawa, Ontario K1S 5B6, Canada
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
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Mayasich SA, Goldsmith MR, Mattingly KZ, LaLone CA. Combining In Vitro and In Silico New Approach Methods to Investigate Type 3 Iodothyronine Deiodinase Chemical Inhibition Across Species. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2023; 42:1032-1048. [PMID: 36825751 PMCID: PMC10895443 DOI: 10.1002/etc.5591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
New approach methodologies (NAMs) are being developed to reduce and replace vertebrate animal testing in support of ecotoxicology and risk assessment. The US Environmental Protection Agency's Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) bioinformatic tool was used to evaluate amino acid sequence conservation of the type 3 iodothyronine deiodinase (DIO3) enzyme across species to demonstrate NAM applications for understanding effects of chemical interactions with a specific protein target. Existing literature was used to identify critical amino acids for thyroid hormone binding and interaction with a reducing cofactor. The SeqAPASS tool identifies whether known critical amino acids involved in ligand binding are exact, partial, or not matches across species compared with a template species based on molecular weight and side chain classification. This evaluation guided the design of variant proteins representing critical amino acid substitutions found in various species. Site-directed mutagenesis of the wild-type (WT) human DIO3 gene sequence was used to create six variant proteins expressed in cell culture, which were then tested in vitro for chemical inhibition. Significant differences in in vitro median inhibitory concentration results were observed among variants for potential competitive inhibitors. A molecular model representing the WT human DIO3 was constructed using Molecular Operating Environment (MOE) software and mutated in silico to create the six variants. The MOE Site Finder tool identified the proposed catalytic and cofactor sites and potential alternative binding sites. Virtual docking did not provide affinity scores with sufficient resolution to rank the potency of the chemical inhibitors. Chemical characteristics, function and location of substituted amino acids, and complexities of the protein target are important considerations in developing NAMs to evaluate chemical susceptibility across species. Environ Toxicol Chem 2023;42:1032-1048. © 2023 University of Wisconsin-Madison. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
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Affiliation(s)
- Sally A. Mayasich
- Aquatic Sciences Center, University of Wisconsin‐Madison, Madison, Wisconsin, USA
- Office of Research and Development, Center for Computational Toxicology and Ecology, Great Lakes Toxicology and Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
| | - Michael R. Goldsmith
- Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, North Carolina
- Congruence Therapeutics, Montreal, Quebec, Canada
| | | | - Carlie A. LaLone
- Office of Research and Development, Center for Computational Toxicology and Ecology, Great Lakes Toxicology and Ecology Division, US Environmental Protection Agency, Duluth, Minnesota
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Finlayson KA, van de Merwe JP, Leusch FDL. Review of ecologically relevant in vitro bioassays to supplement current in vivo tests for whole effluent toxicity testing - Part 2: Non-apical endpoints. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 851:158094. [PMID: 35987232 DOI: 10.1016/j.scitotenv.2022.158094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 08/03/2022] [Accepted: 08/13/2022] [Indexed: 06/15/2023]
Abstract
Whole effluent toxicity (WET) testing uses whole animal exposures to assess the toxicity of complex mixtures, like wastewater. These assessments typically include four apical endpoints: mortality, growth, development, and reproduction. In the last decade, there has been a shift to alternative methods that align with the 3Rs to replace, reduce, and refine the use of animals in research. In vitro bioassays can provide a cost-effective, high-throughput, ethical alternative to in vivo assays. In addition, they can potentially include additional, more sensitive, environmentally relevant endpoints than traditional toxicity tests. However, the ecological relevance of these endpoints must be established before they are adopted into regulatory frameworks. This is Part 2 of a two-part review that aims to identify in vitro bioassays that are linked to ecologically relevant endpoints that could be included in WET testing. Part 2 of this review focuses on non-apical endpoints that should be incorporated into WET testing. In addition to the four apical endpoints addressed in Part 1, this review identified seven additional toxic outcomes: endocrine disruption, xenobiotic metabolism, carcinogenicity, oxidative stress, inflammation, immunotoxicity and neurotoxicity. For each, the response at the molecular or cellular level measured in vitro was linked to the response at the organism level through a toxicity pathway. Literature from 2015 to 2020 was used to identify suitable bioassays that could be incorporated into WET testing.
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Affiliation(s)
| | - Jason P van de Merwe
- Australian Rivers Institute, Griffith University, Australia; School of Environment and Science, Griffith University, Gold Coast, Australia
| | - Frederic D L Leusch
- Australian Rivers Institute, Griffith University, Australia; School of Environment and Science, Griffith University, Gold Coast, Australia
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Jackman SH, Evans EP, Kuecks-Winger HN, Corrie LM, Imbery JJ, Miliano RC, Robert BJ, Thompson VC, Thambirajah AA, Lesperance ML, Pyle GG, van Aggelen G, Helbing CC. Comparison of transcriptome responses of the liver, tail fin, and olfactory epithelium of Rana [Lithobates] catesbeiana tadpoles disrupted by thyroid hormones and estrogen. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 253:106344. [PMID: 36334376 DOI: 10.1016/j.aquatox.2022.106344] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Revised: 10/10/2022] [Accepted: 10/27/2022] [Indexed: 06/16/2023]
Abstract
Thyroid hormones (THs) are important developmental regulators in vertebrates, including during the metamorphosis of a tadpole into a frog. Metamorphosis is a post-embryonic developmental period initiated by TH production in the tadpole thyroid gland. The two main bioactive forms of TH are L-thyroxine (T4) and 3,5,3'-triiodothyronine (T3); these hormones have overlapping but distinct mechanisms of action. Premetamorphic tadpoles are highly responsive to TH and can be induced to metamorphose through exogenous TH exposure, making them an important model for both the study of vertebrate TH signaling and endocrine disrupting chemicals (EDCs). It is important to differentiate TH-mediated responses from estrogenic responses in premetamorphic tadpoles when assessing dysregulation by EDCs as crosstalk between the two endocrine systems is well-documented. Herein, we compare the RNA-sequencing-derived transcriptomic profiles of three TH-responsive tissues (liver, olfactory epithelium, and tail fin) in premetamorphic bullfrog (Rana [Lithobates] catesbeiana) tadpoles exposed to T3, T4, and estradiol (E2). These profiles were generated using the latest available genome assembly for the species. The data indicate that there is a clear distinction, and little overlap, between the transcriptomic responses elicited by E2 and the THs. In contrast, within the THs, the T3- and T4-induced transcriptomic profiles generally show considerable overlap; however, the degree of overlap is highly tissue-dependent, illustrating the importance of distinguishing the two THs and the affected signaling pathways within the target tissue type when evaluating hormone active agents. The data herein also show that E2 and TH treatment can uniquely induce significant changes in expression of their respective "classic" bioindicator transcripts vtg (E2) and thra, thrb, and thibz (THs). However, care must be taken in the interpretation of increased vep or esr1 transcripts as a change in transcript levels can be induced by THs rather than solely E2.
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Affiliation(s)
- Shireen H Jackman
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Ellis P Evans
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Haley N Kuecks-Winger
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Lorissa M Corrie
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Jacob J Imbery
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Rachel C Miliano
- Environment and Climate Change Canada, Pacific Environmental Science Centre, 2645 Dollarton Highway, North Vancouver, British Columbia V7H 1V2, Canada
| | - Bonnie J Robert
- Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Vanessa C Thompson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Anita A Thambirajah
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Mary L Lesperance
- Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Gregory G Pyle
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Graham van Aggelen
- Environment and Climate Change Canada, Pacific Environmental Science Centre, 2645 Dollarton Highway, North Vancouver, British Columbia V7H 1V2, Canada
| | - Caren C Helbing
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada.
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Haselman JT, Olker JH, Kosian PA, Korte JJ, Denny JS, Tietge JE, Hornung MW, Degitz SJ. Characterization of the mechanistic linkages between iodothyronine deiodinase inhibition and impaired thyroid-mediated growth and development in Xenopus laevis using iopanoic acid. Toxicol Sci 2022; 187:139-149. [PMID: 35179606 PMCID: PMC9254162 DOI: 10.1093/toxsci/kfac014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Iodothyronine deiodinases (DIO) are key enzymes that influence tissue-specific thyroid hormone levels during thyroid-mediated amphibian metamorphosis. Within the larger context of evaluating chemicals for thyroid system disrupting potential, chemical activity toward DIOs is being evaluated using high-throughput in vitro screening assays as part of U.S. EPA's ToxCast program. However, existing data gaps preclude any inferences between in vitro chemical inhibition of DIOs and in vivo outcomes relevant to ecological risk assessment. This study aimed to generate targeted data in a laboratory model species (Xenopus laevis) using a model DIO inhibitor, iopanoic acid (IOP), to characterize linkages between in vitro potency, in vivo biochemical responses, and adverse organismal outcomes. In vitro potency of IOP toward DIOs was evaluated using previously developed in vitro screening assays, which showed concentration-dependent inhibition of human DIO1 (IC50: 97 µM) and DIO2 (IC50: 231 µM) but did not inhibit human or X. laevis DIO3 under the assay conditions. In vivo exposure of larval X. laevis to 0, 2.6, 5.3 and 10.5 µM IOP caused thyroid-related biochemical profiles in the thyroid gland and plasma consistent with hyperthyroxinemia but resulted in delayed metamorphosis and significantly reduced growth in the highest two exposure concentrations. Independent evaluations of dio gene expression ontogeny, together with existing literature, supported interpretation of IOP-mediated effects resulting in a proposed adverse outcome pathway for DIO2 inhibition leading to altered amphibian metamorphosis. This study highlights the types of mechanistic data needed to move toward predicting in vivo outcomes of regulatory concern from in vitro bioactivity data.
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Affiliation(s)
- Jonathan T Haselman
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Jennifer H Olker
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Patricia A Kosian
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Joseph J Korte
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Jeffrey S Denny
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Joseph E Tietge
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Michael W Hornung
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
| | - Sigmund J Degitz
- Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, U.S. Environmental Protection Agency, Duluth, Minnesota, 55804
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Liu Y, Wang H, Chai L, Li X, Wu M, Wang H. Effects of perchlorate and exogenous T4 exposures on development, metamorphosis and endochondral ossification in Bufo gargarizans larvae. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 242:106036. [PMID: 34818595 DOI: 10.1016/j.aquatox.2021.106036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 11/12/2021] [Accepted: 11/14/2021] [Indexed: 06/13/2023]
Abstract
Several endocrine-disrupting chemicals (EDCs) have been proven to interfere with the physiological function of thyroid hormone (TH), which affected growth and development. However, few studies have investigated the effects of EDCs on TH axis with consequence for skeletal development in amphibians. This study thus examined the potential role of perchlorate and T4 in growth, development and endochondral ossification during metamorphosis of Bufo gargarizans. Our studies showed that NaClO₄ treatment caused weight gain and delayed the developmental stage in B. gargarizans tadpoles, while T4 decreased body size and survival rate, accelerated metamorphic duration and increased the risk of early death. Histological sections suggested that NaClO₄ and T4 treatments caused damages to thyroid tissue, such as decreased thyroid gland size, follicle size, colloid area, the height of follicular epithelial cells and the number of follicles. In addition, the double skeletal staining and RT-qPCR showed that NaClO₄ and T4 treatments inhibited the endochondral ossification by regulating TH synthesis (TRs, Dios) and endochondral ossification-related genes (MMPs, Runxs, VEGFs and VEGFRs) expression levels, which might affect terrestrial locomotion and terrestrial life. Altogether, these thyroid injury and gene expression changes as caused by NaClO₄ and T4 may have an influence on development and endochondral ossification during the metamorphosis of amphibians.
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Affiliation(s)
- Yutian Liu
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Hemei Wang
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Lihong Chai
- School of Water and Environment, Chang'an University, Xi'an 710054, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an 710062, China
| | - Xinyi Li
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Minyao Wu
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Hongyuan Wang
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China.
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9
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Larval metamorphosis is inhibited by methimazole and propylthiouracil that reveals possible hormonal action in the mussel Mytilus coruscus. Sci Rep 2021; 11:19288. [PMID: 34588587 PMCID: PMC8481496 DOI: 10.1038/s41598-021-98930-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 09/16/2021] [Indexed: 11/08/2022] Open
Abstract
Larval metamorphosis in bivalves is a key event for the larva-to-juvenile transformation. Previously we have identified a thyroid hormone receptor (TR) gene that is crucial for larvae to acquire “competence” for the metamorphic transition in the mussel Mytilus courscus (Mc). The mechanisms of thyroid signaling in bivalves are still largely unknown. In the present study, we molecularly characterized the full-length of two iodothyronine deiodinase genes (McDx and McDy). Phylogenetic analysis revealed that deiodinases of molluscs (McDy, CgDx and CgDy) and vertebrates (D2 and D3) shared a node representing an immediate common ancestor, which resembled vertebrates D1 and might suggest that McDy acquired specialized function from vertebrates D1. Anti-thyroid compounds, methimazole (MMI) and propylthiouracil (PTU), were used to investigate their effects on larval metamorphosis and juvenile development in M. coruscus. Both MMI and PTU significantly reduced larval metamorphosis in response to the metamorphosis inducer epinephrine. MMI led to shell growth retardation in a concentration-dependent manner in juveniles of M. coruscus after 4 weeks of exposure, whereas PTU had no effect on juvenile growth. It is hypothesized that exposure to MMI and PTU reduced the ability of pediveliger larvae for the metamorphic transition to respond to the inducer. The effect of MMI and PTU on larval metamorphosis and development is most likely through a hormonal signal in the mussel M. coruscus, with the implications for exploring the origins and evolution of metamorphosis.
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Abstract
Iodothyronine deiodinases are enzymes capable of activating and inactivating thyroid hormones (THs) and have an important role in regulating TH action in tissues throughout the body. Three types of deiodinases (D1, D2, and D3) were originally defined based on their biochemical characteristics. Cloning of the first complementary DNAs in the 1990s (Dio1 in rat and dio2 and dio3 in frog) allowed to confirm the existence of 3 distinct enzymes. Over the years, increasing genomic information revealed that deiodinases are present in all chordates, vertebrates, and nonvertebrates and that they can even be found in some mollusks and annelids, pointing to an ancient origin. Research in nonmammalian models has substantially broadened our understanding of deiodinases. In relation to their structure, we discovered for instance that biochemical properties such as inhibition by 6-propyl-2-thiouracil, stimulation by dithiothreitol, and temperature optimum are subject to variation. Data from fish, amphibians, and birds were key in shifting our view on the relative importance of activating and inactivating deiodination pathways and in showing the impact of D2 and D3 not only in local but also whole body T3 availability. They also led to the discovery of new local functions such as the acute reciprocal changes in D2 and D3 in hypothalamic tanycytes upon photostimulation, involved in seasonal rhythmicity. With the present possibilities for rapid and precise gene silencing in any species of interest, comparative research will certainly further contribute to a better understanding of the importance of deiodinases for adequate TH action, also in humans.
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Affiliation(s)
- Veerle M Darras
- Laboratory of Comparative Endocrinology, Biology Department, KU Leuven, Leuven, Belgium
- Correspondence: Veerle Darras, PhD, Laboratory of Comparative Endocrinology, Biology Department, KU Leuven, Naamsestraat 61, PB 2464, B-3000 Leuven, Belgium.
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11
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Stinckens E, Vergauwen L, Ankley GT, Blust R, Darras VM, Villeneuve DL, Witters H, Volz DC, Knapen D. An AOP-based alternative testing strategy to predict the impact of thyroid hormone disruption on swim bladder inflation in zebrafish. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 200:1-12. [PMID: 29702435 PMCID: PMC6002951 DOI: 10.1016/j.aquatox.2018.04.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 04/13/2018] [Accepted: 04/17/2018] [Indexed: 05/20/2023]
Abstract
The adverse outcome pathway (AOP) framework can be used to help support the development of alternative testing strategies aimed at predicting adverse outcomes caused by triggering specific toxicity pathways. In this paper, we present a case-study demonstrating the selection of alternative in chemico assays targeting the molecular initiating events of established AOPs, and evaluate use of the resulting data to predict higher level biological endpoints. Based on two AOPs linking inhibition of the deiodinase (DIO) enzymes to impaired posterior swim bladder inflation in fish, we used in chemico enzyme inhibition assays to measure the molecular initiating events for an array of 51 chemicals. Zebrafish embryos were then exposed to 14 compounds with different measured inhibition potentials. Effects on posterior swim bladder inflation, predicted based on the information captured by the AOPs, were evaluated. By linking the two datasets and setting thresholds, we were able to demonstrate that the in chemico dataset can be used to predict biological effects on posterior chamber inflation, with only two outliers out of the 14 tested compounds. Our results show how information organized using the AOP framework can be employed to develop or select alternative assays, and successfully forecast downstream key events along the AOP. In general, such in chemico assays could serve as a first-tier high-throughput system to screen and prioritize chemicals for subsequent acute and chronic fish testing, potentially reducing the need for long-term and costly toxicity tests requiring large numbers of animals.
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Affiliation(s)
- Evelyn Stinckens
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium; Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Gerald T Ankley
- United States Environmental Protection Agency, Mid-Continent Ecology Division,6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Ronny Blust
- Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Veerle M Darras
- Laboratory of Comparative Endocrinology, Department of Biology, KU Leuven, Naamsestraat 61, 3000 Leuven, Belgium
| | - Daniel L Villeneuve
- United States Environmental Protection Agency, Mid-Continent Ecology Division,6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Hilda Witters
- Applied Bio & Molecular Systems (ABS), Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium
| | - David C Volz
- Department of Environmental Sciences, University of California, 900 University Ave, Riverside, CA 92521, USA
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
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12
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Sachs LM, Buchholz DR. Frogs model man: In vivo thyroid hormone signaling during development. Genesis 2017; 55. [PMID: 28109053 DOI: 10.1002/dvg.23000] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 11/14/2016] [Accepted: 11/16/2016] [Indexed: 12/25/2022]
Abstract
Thyroid hormone (TH) signaling comprises TH transport across cell membranes, metabolism by deiodinases, and molecular mechanisms of gene regulation. Proper TH signaling is essential for normal perinatal development, most notably for neurogenesis and fetal growth. Knowledge of perinatal TH endocrinology needs improvement to provide better treatments for premature infants and endocrine diseases during gestation and to counteract effects of endocrine disrupting chemicals. Studies in amphibians have provided major insights to understand in vivo mechanisms of TH signaling. The frog model boasts dramatic TH-dependent changes directly observable in free-living tadpoles with precise and easy experimental control of the TH response at developmental stages comparable to fetal stages in mammals. The hormones, their receptors, molecular mechanisms, and developmental roles of TH signaling are conserved to a high degree in humans and amphibians, such that with respect to developmental TH signaling "frogs are just little people that hop." The frog model is exceptionally illustrative of fundamental molecular mechanisms of in vivo TH action involving TH receptors, transcriptional cofactors, and chromatin remodeling. This review highlights the current need, recent successes, and future prospects using amphibians as a model to elucidate molecular mechanisms and functional roles of TH signaling during post-embryonic development.
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Affiliation(s)
- Laurent M Sachs
- UMR 7221 CNRS, Muséum National d'histoire Naturelle, Dépt. Régulation, Développement et Diversité Moléculaire, Sorbonne Universités, Paris, 75005, France
| | - Daniel R Buchholz
- Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio, 45221
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Chai L, Wang H, Zhao H, Deng H. Chronic effects of triclosan on embryonic development of Chinese toad, Bufo gargarizans. ECOTOXICOLOGY (LONDON, ENGLAND) 2016; 25:1600-1608. [PMID: 27599820 DOI: 10.1007/s10646-016-1715-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/17/2016] [Indexed: 06/06/2023]
Abstract
Triclosan (TCS) is commonly used worldwide in a range of personal care and sanitizing products. The aim of this study was to evaluate potential effects of TCS exposure on embryonic development of Bufo gargarizans, an endemic frog species in China. Standard Gosner stage 3 B. gargarizans embryos were exposed to 10 ~ 150 μg/L TCS during embryogenesis. Survival, total length, weight, developmental stage, duration of different embryo stages, malformation, and type II and III deiodinase (D2 and D3) expression were measured. Inhibitory effects on embryo developmental stage, total length and weight were found at 30 ~ 150 μg/L TCS. Moreover, the duration of embryonic development was increased at gastrula, neural, circulation, and operculum development stage in TCS-treated groups. In addition, TCS exposure induced morphological malformations in B. gargarizans embryos, which are characterized by hyperplasia, abdominal edema, and axial flexures. Furthermore, our results showed that the expression of D2 in embryos was probably down-regulated at 60 and 150 μg/L TCS, but its spatial expression patterns was not affected by TCS. In summary, our study suggested that TCS exposure not only resulted in delayed growth and development but also caused teratogenic effects in B. gargarizans embryos, and the developmental effects of TCS at high concentrations may be associated with disruption of THs homeostasis. Although further studies are necessary, the present findings could provide a basis for understanding on harmful effects and the potential mechanisms of TCS in amphibian embryos.
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Affiliation(s)
- Lihong Chai
- School of Environmental Science and Engineering, Chang'an University, Xi'an, 710054, China
- Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an, 710054, China
| | - Hongyuan Wang
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, China.
| | - Hongfeng Zhao
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, China
| | - Hongzhang Deng
- School of Environmental Science and Engineering, Chang'an University, Xi'an, 710054, China
- Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an, 710054, China
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14
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Houbrechts AM, Delarue J, Gabriëls IJ, Sourbron J, Darras VM. Permanent Deiodinase Type 2 Deficiency Strongly Perturbs Zebrafish Development, Growth, and Fertility. Endocrinology 2016; 157:3668-81. [PMID: 27580812 DOI: 10.1210/en.2016-1077] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Iodothyronine deiodinases are selenocysteine-containing enzymes that activate or inactivate thyroid hormones (THs). Deiodinase type 2 (Dio2) catalyzes the conversion of the prohormone T4 into the transcriptionally active T3 and is the predominant activating deiodinase in zebrafish. Using zinc finger nucleases, we generated two different dio2(-/-) mutant zebrafish lines to investigate the physiological function of this TH activator. The first line contains a deletion of 9 bp, resulting in an in-frame elimination of three conserved amino acids. The other line is characterized by an insertion of 4 bp, leading to the introduction of a premature stop-codon. Both lines completely lack Dio2 activity, resulting in a strong reduction of T3 abundancy in all tissues tested. Early development is clearly perturbed in these animals, as shown by a diverse set of morphometric parameters, defects in swim bladder inflation, and disturbed locomotor activity tested between 1 and 7 days after fertilization. Permanent Dio2 deficiency also provokes long-term effects because growth and especially fertility are severely hampered. Possible compensatory mechanisms were investigated in adult dio2(-/-) mutants, revealing a down-regulation of the inactivating deiodinase Dio3 and TH receptor transcript levels. As the first nonmammalian model with permanent Dio2 deficiency, these mutant zebrafish lines provide evidence that Dio2 is essential to assure normal development and to obtain a normal adult phenotype.
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Affiliation(s)
- Anne M Houbrechts
- Laboratory of Comparative Endocrinology (A.M.H., J.D., I.J.G., V.M.D.), Department of Biology, Division of Animal Physiology and Neurobiology, and Laboratory for Molecular Biodiscovery (J.S.), Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, B-3000, Leuven, Belgium
| | - Julie Delarue
- Laboratory of Comparative Endocrinology (A.M.H., J.D., I.J.G., V.M.D.), Department of Biology, Division of Animal Physiology and Neurobiology, and Laboratory for Molecular Biodiscovery (J.S.), Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, B-3000, Leuven, Belgium
| | - Isabelle J Gabriëls
- Laboratory of Comparative Endocrinology (A.M.H., J.D., I.J.G., V.M.D.), Department of Biology, Division of Animal Physiology and Neurobiology, and Laboratory for Molecular Biodiscovery (J.S.), Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, B-3000, Leuven, Belgium
| | - Jo Sourbron
- Laboratory of Comparative Endocrinology (A.M.H., J.D., I.J.G., V.M.D.), Department of Biology, Division of Animal Physiology and Neurobiology, and Laboratory for Molecular Biodiscovery (J.S.), Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, B-3000, Leuven, Belgium
| | - Veerle M Darras
- Laboratory of Comparative Endocrinology (A.M.H., J.D., I.J.G., V.M.D.), Department of Biology, Division of Animal Physiology and Neurobiology, and Laboratory for Molecular Biodiscovery (J.S.), Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, B-3000, Leuven, Belgium
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15
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Lorenz C, Opitz R, Trubiroha A, Lutz I, Zikova A, Kloas W. The synthetic gestagen levonorgestrel directly affects gene expression in thyroid and pituitary glands of Xenopus laevis tadpoles. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 177:63-73. [PMID: 27262936 DOI: 10.1016/j.aquatox.2016.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 05/17/2016] [Accepted: 05/19/2016] [Indexed: 06/05/2023]
Abstract
The synthetic gestagen levonorgestrel (LNG) was previously shown to perturb thyroid hormone-dependent metamorphosis in Xenopus laevis. However, so far the mechanisms underlying the anti-metamorphic effects of LNG remained unknown. Therefore, a series of in vivo and ex vivo experiments was performed to identify potential target sites of LNG action along the pituitary-thyroid axis of X. laevis tadpoles. Prometamorphic tadpoles were treated in vivo with LNG (0.01-10nM) for 72h and brain-pituitary and thyroid tissue was analyzed for marker gene expression. While no treatment-related changes were observed in brain-pituitary tissue, LNG treatment readily affected thyroidal gene expression in tadpoles including decreased slc5a5 and iyd mRNA expression and a strong induction of dio2 and dio3 expression. When using an ex vivo organ explant culture approach, direct effects of LNG on both pituitary and thyroid gland gene expression were detecTable Specifically, treatment of pituitary explants with 10nM LNG strongly stimulated dio2 expression and concurrently suppressed tshb expression. In thyroid glands, ex vivo LNG treatment induced dio2 and dio3 mRNA expression in a thyrotropin-independent manner. When thyroid explants were cultured in thyrotropin-containing media, LNG caused similar gene expression changes as seen after 72h in vivo treatment including a very strong repression of thyrotropin-induced slc5a5 expression. Concerning the anti-thyroidal activity of LNG as seen under in vivo conditions, our ex vivo data provide clear evidence that LNG directly affects expression of genes important for thyroidal iodide handling as well as genes involved in negative feedback regulation of pituitary tshb expression.
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Affiliation(s)
- Claudia Lorenz
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
| | - Robert Opitz
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Institute of Interdisciplinary Research in Molecular Human Biology (IRIBHM), Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium
| | - Achim Trubiroha
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Institute of Interdisciplinary Research in Molecular Human Biology (IRIBHM), Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium
| | - Ilka Lutz
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany
| | - Andrea Zikova
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany
| | - Werner Kloas
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Department of Endocrinology, Institute of Biology, Humboldt University Berlin, Germany
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16
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Maher SK, Wojnarowicz P, Ichu TA, Veldhoen N, Lu L, Lesperance M, Propper CR, Helbing CC. Rethinking the biological relationships of the thyroid hormones, l-thyroxine and 3,5,3′-triiodothyronine. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2016; 18:44-53. [DOI: 10.1016/j.cbd.2016.04.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 03/27/2016] [Accepted: 04/03/2016] [Indexed: 11/16/2022]
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17
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Wang C, Liang G, Chai L, Wang H. Effects of copper on growth, metamorphosis and endocrine disruption of Bufo gargarizans larvae. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 170:24-30. [PMID: 26587739 DOI: 10.1016/j.aquatox.2015.10.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/30/2015] [Accepted: 10/31/2015] [Indexed: 05/09/2023]
Abstract
Chinese toad (Bufo gargarizans) tadpoles were exposed to copper (1, 6.4, 32 and 64μgL(-1) copper) from the beginning of larval period through completion of metamorphosis. We examined the effects of chronic copper exposure on mortality, growth, time to metamorphosis, tail resorption time, body size at the metamorphic climax (Gs 42) and completion of metamorphosis (Gs 46) and thyroid gland histology. In addition, type 2 and 3 iodothyronine deiodinase (Dio2 and Dio3), thyroid hormone receptors (TRα and TRβ) mRNA levels were also measured to assess disruption of TH synthesis. Our result showed that 6.4-64μgL(-1) copper concentration increased the mortality and inhibited the growth of B. gargarizans tadpoles. In addition, significant reduction in size at Gs 42 and a time delay to Gs 42 were observed at 6.4-64μgL(-1) copper treatments. Moreover, histological examinations have clearly revealed that 64μgL(-1) copper caused follicular cell hyperplasia in thyroid gland. According to real-time PCR results, exposure to 32 and 64μgL(-1) copper significantly up-regulated mRNA expression of Dio3, but down-regulated mRNA expression of TRα and TRβ mRNA level. We concluded that copper delayed amphibian metamorphosis through changing mRNA expression of Dio3, TRα and TRβ, which suggests that copper might have the endocrine-disrupting effect.
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Affiliation(s)
- Chao Wang
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Gang Liang
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China
| | - Lihong Chai
- School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Xi'an 710062, China
| | - Hongyuan Wang
- College of Life Science, Shaanxi Normal University, Xi'an 710119, China.
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18
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Schweizer U, Steegborn C. New insights into the structure and mechanism of iodothyronine deiodinases. J Mol Endocrinol 2015; 55:R37-52. [PMID: 26390881 DOI: 10.1530/jme-15-0156] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/16/2015] [Indexed: 12/30/2022]
Abstract
Iodothyronine deiodinases are a family of enzymes that remove specific iodine atoms from one of the two aromatic rings in thyroid hormones (THs). They thereby fine-tune local TH concentrations and cellular TH signaling. Deiodinases catalyze a remarkable biochemical reaction, i.e., the reductive elimination of a halogenide from an aromatic ring. In metazoans, deiodinases depend on the rare amino acid selenocysteine. The recent solution of the first experimental structure of a deiodinase catalytic domain allowed for a reappraisal of the many mechanistic and mutagenesis data that had been accumulated over more than 30 years. Hence, the structure generates new impetus for research directed at understanding catalytic mechanism, substrate specificity, and regulation of deiodinases. This review will focus on structural and mechanistic aspects of iodothyronine deiodinases and briefly compare these enzymes with dehalogenases, which catalyze related reactions. A general mechanism for the selenium-dependent deiodinase reaction will be described, which integrates the mouse deiodinase 3 crystal structure and biochemical studies. We will summarize further, sometimes isoform-specific molecular features of deiodinase catalysis and regulation, and we will then discuss available compounds for modulating deiodinase activity for therapeutic purposes.
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Affiliation(s)
| | - Clemens Steegborn
- Institut für Biochemie und MolekularbiologieRheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, 53115 Bonn, GermanyLehrstuhl BiochemieUniversität Bayreuth, Universitätsstrasse 30, 95445 Bayreuth, Germany
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19
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Bulaeva E, Lanctôt C, Reynolds L, Trudeau VL, Navarro-Martín L. Sodium perchlorate disrupts development and affects metamorphosis- and growth-related gene expression in tadpoles of the wood frog (Lithobates sylvaticus). Gen Comp Endocrinol 2015; 222:33-43. [PMID: 25623150 DOI: 10.1016/j.ygcen.2015.01.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 12/19/2014] [Accepted: 01/16/2015] [Indexed: 11/20/2022]
Abstract
Numerous endocrine disrupting chemicals can affect the growth and development of amphibians. We investigated the effects of a targeted disruption of the endocrine axes modulating development and somatic growth. Wood frog (Lithobates sylvaticus) tadpoles were exposed for 2weeks (from developmental Gosner stage (Gs) 25 to Gs30) to sodium perchlorate (SP, thyroid inhibitor, 14mg/L), estradiol (E2, known to alter growth and development, 200nM) and a reduced feeding regime (RF, to affect growth and development in a chemically-independent manner). All treatments experienced developmental delay, and animals exposed to SP or subjected to RF respectively reached metamorphic climax (Gs42) approximately 11(±3) and 17(±3) days later than controls. At Gs42, only SP-treated animals showed increased weight and snout-vent length (P<0.05) relative to controls. Tadpoles treated with SP had 10-times higher levels of liver igf1 mRNA after 4days of exposure (Gs28) compared to controls. Tadpoles in the RF treatment expressed 6-times lower levels of liver igf1 mRNA and 2-times higher liver igf1r mRNA (P<0.05) at Gs30. Tadpoles treated with E2 exhibited similar developmental and growth patterns as controls, but had increased liver igf1 mRNA levels at Gs28, and tail igf1r at Gs42. Effects on tail trβ mRNA levels were detected in SP-treated tadpoles at Gs42, 40days post-exposure, suggesting that the chemical inhibition of thyroid hormone production early in development can have long-lasting effects. The growth effects observed in the SP-exposed animals suggest a relationship between TH-dependent development and somatic growth in L. sylvaticus tadpoles.
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Affiliation(s)
- Elizabeth Bulaeva
- Centre for Advanced Research in Environmental Genomics, Biology Department, University of Ottawa, Ontario K1N 6N5, Canada
| | - Chantal Lanctôt
- Centre for Advanced Research in Environmental Genomics, Biology Department, University of Ottawa, Ontario K1N 6N5, Canada
| | - Leslie Reynolds
- Centre for Advanced Research in Environmental Genomics, Biology Department, University of Ottawa, Ontario K1N 6N5, Canada
| | - Vance L Trudeau
- Centre for Advanced Research in Environmental Genomics, Biology Department, University of Ottawa, Ontario K1N 6N5, Canada
| | - Laia Navarro-Martín
- Centre for Advanced Research in Environmental Genomics, Biology Department, University of Ottawa, Ontario K1N 6N5, Canada.
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20
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Navarro-Martín L, Lanctôt C, Jackman P, Park BJ, Doe K, Pauli BD, Trudeau VL. Effects of glyphosate-based herbicides on survival, development, growth and sex ratios of wood frogs (Lithobates sylvaticus) tadpoles. I: chronic laboratory exposures to VisionMax®. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2014; 154:278-90. [PMID: 24878356 DOI: 10.1016/j.aquatox.2014.05.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 05/07/2014] [Accepted: 05/13/2014] [Indexed: 05/06/2023]
Abstract
The purpose of this study was to determine if chronic exposure to the glyphosate-based herbicide VisionMax(®) affects the survival, development, growth, sex ratios and expression of specific genes involved in metamorphosis of wood frog tadpoles (Lithobates sylvaticus). We hypothesized that exposure to this herbicide will affect developmental rates by disrupting hormone pathways, sex ratios and/or gonadal morphology. Tadpoles were chronically exposed in the laboratory from Gosner developmental stage 25 to 42 to four different concentrations of VisionMax(®) (ranging from 0.021 to 2.9 mg acid equivalents/L). Chronic exposures to VisionMax(®) had direct effects on the metamorphosis of L. sylvaticus tadpoles by decreasing development rates, however, there was a decrease in survival only in the group exposed to the highest dose of VisionMax(®) (2.9 mg a.e./L; from approximately 96% in the control group to 77% in the treatment group). There was a decrease in the number of tadpoles reaching metamorphic climax, from 78% in the control group to 42% in the VisionMax(®) (2.9 mg a.e./L) group, and a 7-day delay to reach metamorphic climax in the same treatment group. No effects of exposure on sex ratios or gonadal morphology were detected in tadpoles exposed to any of the concentrations of VisionMax(®) tested. Gene expression analyses in brain and tail tissues demonstrated that exposure to VisionMax(®) alters the expression of key genes involved in development. Results showed significant interaction (two-way ANOVA, P<0.05) between developmental Gosner stage and treatment in brain corticotropin-releasing factor, deiodinase type II (dio2) and glucocorticotiroid receptor (grII) and tail dio2 and grII. This demonstrates that mRNA levels may be differently affected by treatment depending on the developmental stage at which they are assessed. At the same time there was a clear dose-response effect for VisionMax(®) to increase thyroid hormone receptor β in tadpole brain (F(2,69)=3.475, P=0.037) and tail (F(2,69)=27.569, P<0.001), regardless of developmental stage. Interestingly, delays in development (or survival) were only observed in the group exposed to 2.9 mg a.e./L of VisionMax(®), suggesting that tadpoles need to be exposed to a "threshold" concentration of glyphosate-based herbicide to exhibit phenotypic observable effects. We suggest that the upregulation of genes that trigger metamorphosis following VisionMax(®) herbicide exposure might result from a compensatory response for the delays in development observed. Further studies are needed to determine if disruption of expression of these key genes leads to long-term effects when metamorphs reach adult stages.
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Affiliation(s)
- L Navarro-Martín
- Centre for Advanced Research in Environmental Genomics (CAREG), Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
| | - C Lanctôt
- Centre for Advanced Research in Environmental Genomics (CAREG), Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
| | - P Jackman
- Atlantic Laboratory for Environmental Testing, Atlantic Region Environmental Science Centre, Environment Canada, Corner Morton Ave. & University Ave., Moncton, NB E1A 6S8, Canada.
| | - B J Park
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB R3T 2N6, Canada.
| | - K Doe
- Atlantic Laboratory for Environmental Testing, Atlantic Region Environmental Science Centre, Environment Canada, Corner Morton Ave. & University Ave., Moncton, NB E1A 6S8, Canada.
| | - B D Pauli
- National Wildlife Research Centre, Environment Canada, Carleton University, Raven Road, Ottawa, ON K1A 0H3, Canada.
| | - V L Trudeau
- Centre for Advanced Research in Environmental Genomics (CAREG), Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
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21
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Zhao H, Chai L, Wang H. Effects of fluoride on metamorphosis, thyroid and skeletal development in Bufo gargarizans tadpoles. ECOTOXICOLOGY (LONDON, ENGLAND) 2013; 22:1123-32. [PMID: 23934448 DOI: 10.1007/s10646-013-1099-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/22/2013] [Indexed: 06/02/2023]
Abstract
This study examined the effects of chronic fluoride exposure on metamorphosis, thyroid and skeletal development in tadpoles of Chinese Toad, Bufo gargarizans. The tadpoles were exposed to fluoride concentrations either at 0, 1, 5, 10, or at 50 mg L(-1) from Gosner stage 26 to Gosner stage 42. Body weight, total length and percentage of tadpoles reaching metamorphosis climax were recorded, and thyroid histological examinations were employed. In addition, mRNA expression of both deiodinase type 2 (D2) and deiodinase type 3 (D3) was analyzed by using RT-PCR and skeletal systems were investigated by using double-staining methodology at stage 42. Results showed that total length and body weight were unaffected by fluoride exposure at all concentrations while metamorphosis was strongly inhibited only by 50 mg L(-1) fluoride. Histomorphological measurements showed the percentage of colloid depletion in thyroid gland increased significantly, while the average diameter of follicles was significantly shorter at 50 mg L(-1) concentration. In addition, fluoride at 5 mg L(-1) can stimulate bone mineralization, while fluoride at 50 mg L(-1) can retard deposition of calcium. In conclusion, our study suggests that 50 mg L(-1) fluoride could damage follicular cells in thyroid gland and induce a sharp reduction in thyroid hormone probably through the up-regulation of D3 mRNA expression, and these influences on thyroid system may delay metamorphosis as well as ossification in bone tissue by inhibiting calcium deposition.
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Affiliation(s)
- Hongfeng Zhao
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, People's Republic of China
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Orozco A, Valverde-R C, Olvera A, García-G C. Iodothyronine deiodinases: a functional and evolutionary perspective. J Endocrinol 2012; 215:207-19. [PMID: 22872760 DOI: 10.1530/joe-12-0258] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
From an evolutionary perspective, deiodinases may be considered pivotal players in the emergence and functional diversification of both thyroidal systems (TS) and their iodinated messengers. To better understand the evolutionary pathway and the concomitant functional diversification of vertebrate deiodinases, in the present review we summarized the highlights of the available information regarding this ubiquitous enzymatic component that represents the final, common physiological link of TS. The information reviewed here suggests that deiodination of tyrosine metabolites is an ancient feature of all chordates studied to date and consequently, that it precedes the integration of the TS that characterize vertebrates. Phylogenetic analysis presented here points to D1 as the oldest vertebrate deiodinase and to D2 as the most recent deiodinase gene, a hypothesis that agrees with the notion that D2 is the most specialized and finely regulated member of the family and plays a key role in vertebrate neurogenesis. Thus, deiodinases seem to be major participants in the evolution and functional expansion of the complex regulatory network of TS found in vertebrates.
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Affiliation(s)
- Aurea Orozco
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla, Juriquilla, Querétaro, México.
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Abstract
Iodothyronine deiodinases are important mediators of thyroid hormone (TH) action. They are present in tissues throughout the body where they catalyse 3,5,3'-triiodothyronine (T(3)) production and degradation via, respectively, outer and inner ring deiodination. Three different types of iodothyronine deiodinases (D1, D2 and D3) have been identified in vertebrates from fish to mammals. They share several common characteristics, including a selenocysteine residue in their catalytic centre, but show also some type-specific differences. These specific characteristics seem very well conserved for D2 and D3, while D1 shows more evolutionary diversity related to its Km, 6-n-propyl-2-thiouracil sensitivity and dependence on dithiothreitol as a cofactor in vitro. The three deiodinase types have an impact on systemic T(3) levels and they all contribute directly or indirectly to intracellular T(3) availability in different tissues. The relative contribution of each of them, however, varies amongst species, developmental stages and tissues. This is especially true for amphibians, where the impact of D1 may be minimal. D2 and D3 expression and activity respond to thyroid status in an opposite and conserved way, while the response of D1 is variable, especially in fish. Recently, a number of deiodinases have been cloned from lower chordates. Both urochordates and cephalochordates possess selenodeiodinases, although they cannot be classified in one of the three vertebrate types. In addition, the cephalochordate amphioxus also expresses a non-selenodeiodinase. Finally, deiodinase-like sequences have been identified in the genome of non-deuterostome organisms, suggesting that deiodination of externally derived THs may even be functionally relevant in a wide variety of invertebrates.
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Affiliation(s)
- Veerle M Darras
- Animal Physiology and Neurobiology Section, Department of Biology, Laboratory of Comparative Endocrinology, KU Leuven, Leuven, Belgium.
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Fini JB, Le Mével S, Palmier K, Darras VM, Punzon I, Richardson SJ, Clerget-Froidevaux MS, Demeneix BA. Thyroid hormone signaling in the Xenopus laevis embryo is functional and susceptible to endocrine disruption. Endocrinology 2012; 153:5068-81. [PMID: 22968643 DOI: 10.1210/en.2012-1463] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (TH) is essential for vertebrate brain development. Most research on TH and neuronal development focuses on late development, mainly the perinatal period in mammals. However, in human infants neuromotor development correlates best with maternal TH levels in the first trimester of pregnancy, suggesting that TH signaling could affect early brain development. Studying TH signaling in early embryogenesis in mammals is experimentally challenging. In contrast, free-living embryos, such as Xenopus laevis, permit physiological experimentation independent of maternal factors. We detailed key elements of TH signaling: ligands, receptors (TR), and deiodinases during early X. laevis development, before embryonic thyroid gland formation. Dynamic profiles for all components were found. Between developmental stages 37 and 41 (~48 h after hatching, coincident with a phase of continuing neurogenesis) significant increases in T(3) levels as well as in mRNA encoding deiodinases and TR occurred. Exposure of embryos at this developmental stage for 24 h to either a TH antagonist, NH-3, or to tetrabromobisphenol A, a flame retardant and known TH disruptor, differentially modulated the expression of a number of TH target genes implicated in neural stem cell function or neural differentiation. Moreover, 24-h exposure to either NH-3 or tetrabromobisphenol A diminished cell proliferation in the brain. Thus, these data show first, that TH signaling exerts regulatory roles in early X. laevis neurogenesis and second, that this period represents a potential window for endocrine disruption.
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Affiliation(s)
- J B Fini
- Unité Mixte de Recherche Centre National de la Recherche Scientifique 7221, Evolution des Régulations Endocriniennes CNRS UMR 7221/Muséum National d'Histoire Naturelle Département Régulations, Développement et Diversité Moléculaire, 75231 Paris, France
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Zhu B, Shrivastava A, Luongo C, Chen T, Harney JW, Marsili A, Tran TV, Bhadouria A, Mopala R, Steen AI, Larsen PR, Zavacki AM. Catalysis leads to posttranslational inactivation of the type 1 deiodinase and alters its conformation. J Endocrinol 2012; 214:87-94. [PMID: 22544951 PMCID: PMC3612969 DOI: 10.1530/joe-11-0459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Previously, it was shown that the type 1 deiodinase (D1) is subject to substrate-dependent inactivation that is blocked by pretreatment with the inhibitor of D1 catalysis, propylthiouracil (PTU). Using HepG2 cells with endogenous D1 activity, we found that while considerable D1-mediated catalysis of reverse tri-iodothyronine (rT(3)) is observed in intact cells, there was a significant loss of D1 activity in sonicates assayed from the same cells in parallel. This rT(3)-mediated loss of D1 activity occurs despite no change in D1 mRNA levels and is blocked by PTU treatment, suggesting a requirement for catalysis. Endogenous D1 activity in sonicates was inactivated in a dose-dependent manner in HepG2 cells, with a ∼50% decrease after 10 nM rT(3) treatment. Inactivation of D1 was rapid, occurring after only half an hour of rT(3) treatment. D1 expressed in HEK293 cells was inactivated by rT(3) in a similar manner. (75)Se labeling of the D1 selenoprotein indicated that after 4 h rT(3)-mediated inactivation of D1 occurs without a corresponding decrease in D1 protein levels, though rT(3) treatment causes a loss of D1 protein after 8-24 h. Bioluminescence resonance energy transfer studies indicate that rT(3) exposure increases energy transfer between the D1 homodimer subunits, and this was lost when the active site of D1 was mutated to alanine, suggesting that a post-catalytic structural change in the D1 homodimer could cause enzyme inactivation. Thus, both D1 and type 2 deiodinase are subject to catalysis-induced loss of activity although their inactivation occurs via very different mechanisms.
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Affiliation(s)
- Bo Zhu
- Division of Endocrinology, Diabetes and Hypertension, Thyroid Section, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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Klootwijk W, Friesema ECH, Visser TJ. A nonselenoprotein from amphioxus deiodinates triac but not T3: is triac the primordial bioactive thyroid hormone? Endocrinology 2011; 152:3259-67. [PMID: 21652724 DOI: 10.1210/en.2010-1408] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (TH) is important for metamorphosis in many species, including the cephalochordate Branchiostoma floridae, a marine invertebrate (amphioxus) living in warmer coastal areas. Branchiostoma expresses a TH receptor, which is activated by 3,3',5-triiodothyroacetic acid (TA(3)) but not by T(3). The Branchiostoma genome also contains multiple genes coding for proteins homologous to iodothyronine deiodinases in vertebrates, selenoproteins catalyzing the activation or inactivation of TH. Three Branchiostoma deiodinases have been cloned: two have a catalytic Sec, and one, bfDy, has a Cys residue. We have studied the catalytic properties of bfDy in transfected COS1 cells by HPLC analysis of reactions with (125)I-labeled substrates and dithiothreitol as cofactor. We could not detect deiodination of T(4), T(3), or rT(3) by bfDy but observed rapid and selective inner ring deiodination (inactivation) of TA(3) and 3,3',5,5'-tetraiodothyroacetic acid (TA(4)). Deiodination of TA(3) by bfDy was optimal at 25 C and 10 mm dithiothreitol. bfDy was extremely labile at 37 C, showing a half-life of less than 2 min, in contrast with a half-life of more than 60 min at 25 C. Deiodination of labeled TA(3) was inhibited dose dependently by unlabeled TA(3)≈TA(4)>T(4)≈T(3). Michaelis-Menten analysis yielded Michaelis-Menten constant values of 6.8 and 68 nm and maximum velocity values of 1.4 and 5.4 pmol/min·mg protein for TA(3) and TA(4), respectively. bfDy was not inhibited by propylthiouracil and iodoacetate and only weakly by goldthioglucose and iopanoic acid. In conclusion, we demonstrate rapid inactivation of TA(3) and TA(4) but not of T(3) and T(4) by the first reported natural nonselenodeiodinase. Our findings support the hypothesis that TA(3) is a primordial bioactive TH.
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Affiliation(s)
- Wim Klootwijk
- Department of Internal Medicine, Erasmus University Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
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Bouzaffour M, Rampon C, Ramaugé M, Courtin F, Vriz S. Implication of type 3 deiodinase induction in zebrafish fin regeneration. Gen Comp Endocrinol 2010; 168:88-94. [PMID: 20403357 DOI: 10.1016/j.ygcen.2010.04.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Revised: 03/24/2010] [Accepted: 04/14/2010] [Indexed: 01/28/2023]
Abstract
Thyroid hormones are critical determinants of cellular differentiation. We used the zebrafish model to evaluate the involvement of thyroid hormones in regeneration processes after caudal fin amputation. We examined early events following fin amputation, i.e., blastema formation and nerve repair by growth cone formation. Here, we show that the abolition of thyroid gland activity by methimazole treatment had no effect on blastema formation, but slowed growth cone formation of the lateral line. Conversely, the addition of exogenous thyroid hormones enhanced growth cone formation without affecting blastema formation. However, amputation triggered a strong induction in the blastema of type 3 deiodinase mRNA and enzymatic activity, which degrades thyroid hormone (TH). We therefore blocked deiodinase activity with iopanoic acid (IOP) and saw a reduction in blastema formation, suggesting that local degradation of TH is permissive for cell proliferation in the blastema. The effect of IOP on the blastema required endogenous or exogenous TH. Our findings support a model in which local degradation of TH by type 3 deiodinase is permissive for epimorphic regeneration.
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Duarte-Guterman P, Langlois VS, Pauli BD, Trudeau VL. Expression and T3 regulation of thyroid hormone- and sex steroid-related genes during Silurana (Xenopus) tropicalis early development. Gen Comp Endocrinol 2010; 166:428-35. [PMID: 20015451 DOI: 10.1016/j.ygcen.2009.12.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 12/01/2009] [Accepted: 12/05/2009] [Indexed: 11/26/2022]
Abstract
In amphibians, thyroid hormones (THs) are the primary regulators of metamorphosis; however, their physiological role during embryogenesis remains unclear. First, we established complete developmental profiles for TH receptors (tr alpha and tr beta), deiodinases (dio; types 1, 2, 3), estrogen receptors (er alpha and er beta) and androgen receptor (ar) mRNA levels during embryogenesis and early larval stages in Silurana (Xenopus) tropicalis (from Nieuwkoop and Faber (NF) stage 2 until NF 46). Real-time RT-PCR analyses in whole embryos and larvae revealed that all transcripts except tr alpha were detected throughout development; tr alpha only appears after gastrulation. The first significant increase in the expression of tralpha and tr beta was observed before hatching, between NF 21 and NF 27 (2.5- and 11-fold, respectively). In order to test if these genes could be regulated by THs during early larval development, embryos were exposed to triiodothyronine (T3; 0.5, 5.0, 50 nM) from NF 27 to NF 46. T3 exposure caused a dose-dependent increase relative to control in the expression of tr alpha, tr beta, dio (types 2 and 3), ar, and 5 alpha-reductase type 1 in whole larvae. These results indicate that in S. tropicalis, tr and dio can be induced by T3 as early as NF 46, a response that had only been characterized later during frog metamorphosis. In addition, T3 also affected androgen-related gene expression, supporting our hypothesis that THs are involved in male development in frogs.
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Affiliation(s)
- Paula Duarte-Guterman
- Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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Croteau MC, Davidson M, Duarte-Guterman P, Wade M, Popesku JT, Wiens S, Lean DRS, Trudeau VL. Assessment of thyroid system disruption in Rana pipiens tadpoles chronically exposed to UVB radiation and 4-tert-octylphenol. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2009; 95:81-92. [PMID: 19811842 DOI: 10.1016/j.aquatox.2009.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2008] [Revised: 05/07/2009] [Accepted: 05/27/2009] [Indexed: 05/28/2023]
Abstract
Many studies have considered recent increases in ultraviolet B radiation (UVBR) and endocrine disrupting chemicals polluting the environment as possible contributing factors to the reduction in amphibian populations. It has been demonstrated that exposure of amphibians to estrogenic chemicals or UVBR can affect the timing of larval development and metamorphosis. However, amphibians in the wild are exposed to multiple environmental stressors simultaneously. Therefore, our study examines the effects of UVBR and the estrogenic chemical 4-tert-octylphenol (OP), alone and in combination, on the thyroid system of Rana pipiens tadpoles, which is the main regulator of amphibian metamorphosis. Results demonstrate that thyroid gland histomorphology measurements in Gosner stage 31 tadpoles continuously exposed to UVBR (0.21W/m(2)) were not different than those measured in animals from the control group. In a separate experiment, tadpoles exposed to environmentally relevant levels of UVBR (0.22W/m(2)) and/or OP (0.01nM or 10nM) exhibited significantly delayed development starting from Gosner stage 29, given that fewer tadpoles developed past stage 29 in these groups. In addition, significantly fewer UVBR-treated tadpoles developed past stage 34 and metamorphosed. Samples were collected from stages 29 and 34 tadpoles for gene expression analysis in tail tissue and measurements of T3 (triiodothyronine) whole body levels (minus tail). UVBR and/or OP exposure did not affect T3 levels in stages 29 and 34 tadpoles. However, a decrease in deiodinase type 2 (D2) or increase in deiodinase type 3 (D3) mRNA levels was observed in groups of tadpoles with slowed developmental rates at those developmental stages. Given that D2 activates and D3 inactivates thyroid hormones (TH), UVBR/OP mediated disruptions in development are likely caused by dysfunctions in the localized metabolism of THs through alterations in the expression of these enzymes in peripheral tissues. This is the first study to our knowledge reporting a potential thyroid-based mechanism of action for the developmental delays in amphibians exposed to UVBR and/or OP.
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Affiliation(s)
- M C Croteau
- Centre for Advanced Research in Environmental Genomics (CAREG), Department of Biology, University of Ottawa, 20 Marie Curie Street, Ottawa, Ontario, Canada, K1N 6N5.
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31
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Levitan DR, Stapper AP. Simultaneous positive and negative frequency-dependent selection on sperm bindin, a gamete recognition protein in the sea urchin Strongylocentrotus purpuratus. Evolution 2009; 64:785-97. [PMID: 19796148 DOI: 10.1111/j.1558-5646.2009.00850.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Gamete-recognition proteins often, but not always, evolve rapidly. We explored how variation in sperm bindin influences reproductive success of the sea urchin Strongylocentrotus purpuratus during group spawning in the sea. Despite large variation in male and female abundance and neighbor distances, males with common genotypes had higher reproductive success than males with rare genotypes. However, males with a relatively uncommon proline-for-serine substitution were the most successful. Females also showed a fitness consequence of sperm-bindin genotype, suggesting linkage disequilibrium between the sperm-bindin locus and the egg receptor locus. Females with common genotypes had higher reproductive success than rare genotypes, but females with relatively uncommon insertions were most successful. Overall, these results suggest that rare male proteins are selected against, as supported by molecular evidence of purifying selection and probably caused by poor matches to the female receptor protein. Within the pool of moderately common to common alleles, however, individuals with less-common functional variants were favored and probably maintained by negative frequency-dependent selection. These results support the hypothesis that sperm availability and sexual conflict influence the evolution of gamete recognition systems in broadcast spawners and highlight the benefits of combining fitness measures with molecular signatures for estimation of patterns of selection.
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Affiliation(s)
- Don R Levitan
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA.
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Lorenz C, Opitz R, Lutz I, Kloas W. Corticosteroids disrupt amphibian metamorphosis by complex modes of action including increased prolactin expression. Comp Biochem Physiol C Toxicol Pharmacol 2009; 150:314-21. [PMID: 19481173 DOI: 10.1016/j.cbpc.2009.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 05/18/2009] [Accepted: 05/19/2009] [Indexed: 10/20/2022]
Abstract
Although thyroid hormones (TH) are the primary morphogens regulating amphibian metamorphosis, other hormones including corticosteroids are known to participate in this regulation. The present study investigated effects of corticosteroids on larval development of the amphibian Xenopus laevis. Premetamorphic tadpoles (stage 51) were treated with aldosterone (ALDO; 100 nM), corticosterone (B; 10, 100, 500 nM) and dexamethasone (DEX; 10, 100, 500 nM) for 21 days and organismal responses were assessed by gross morphology determining stage development, whole body length (WBL), and hind limb length (HLL). B and DEX reduced WBL and HLL and caused abnormal development including the lack of fore limb emergence while ALDO treatment showed no significant effect. Gene expression analyses using RT-PCR revealed up-regulation of prolactin (PRL) in brain, but down-regulation of type III deiodinase in tail tissue induced by the glucocorticoids B and DEX. Additionally, stromelysin-3 transcript in tail tissue was decreased by B. ALDO at 100 nM had no effect on mRNA expression, neither in brain nor in tail tissue. These findings indicate that corticosteroids modulate TH-dependent metamorphosis by complex mechanisms that even include indirect effects triggered by increased PRL mRNA expression.
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Affiliation(s)
- Claudia Lorenz
- Department of Aquaculture and Ecophysiology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
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Croteau MC, Davidson MA, Lean DRS, Trudeau VL. Global Increases in Ultraviolet B Radiation: Potential Impacts on Amphibian Development and Metamorphosis. Physiol Biochem Zool 2008; 81:743-61. [PMID: 18954263 DOI: 10.1086/591949] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- M C Croteau
- Center for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, 20 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.
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