scholarly journals Both thyroid hormone and 9-cis retinoic acid receptors are required to efficiently mediate the effects of thyroid hormone on embryonic development and specific gene regulation in Xenopus laevis.

1997 ◽  
Vol 17 (8) ◽  
pp. 4738-4749 ◽  
Author(s):  
M Puzianowska-Kuznicka ◽  
S Damjanovski ◽  
Y B Shi
Keyword(s):  
Retinoic Acid ◽  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Hormone Receptors ◽  
Biological Effects ◽  
Retinoic Acid Receptors ◽  
Specific Gene ◽  
Xenopus Embryos

Tissue culture transfection and in vitro biochemical studies have suggested that heterodimers of thyroid hormone receptors (TRs) and 9-cis retinoic acid receptors (RXRs) are the likely in vivo complexes that mediate the biological effects of thyroid hormone, 3,5,3'-triiodothyronine (T3). However, direct in vivo evidence for such a hypothesis has been lacking. We have previously reported a close correlation between the coordinated expression of TR and RXR genes and tissue-dependent temporal regulation of organ transformations during Xenopus laevis metamorphosis. By introducing TRs and RXRs either individually or together into developing Xenopus embryos, we demonstrate here that RXRs are critical for the developmental function of TRs. Precocious expression of TRs and RXRs together but not individually leads to drastic, distinct embryonic abnormalities, depending upon the presence or absence of T3, and these developmental effects require the same receptor domains as those required for transcriptional regulation by TR-RXR heterodimers. More importantly, the overexpressed TR-RXR heterodimers faithfully regulate endogenous T3 response genes that are normally regulated by T3 only during metamorphosis. That is, they repress the genes in the absence of T3 and activate them in the presence of the hormone. On the other hand, the receptors have no effect on a retinoic acid (RA) response gene. Thus, RA- and T3 receptor-mediated teratogenic effects in Xenopus embryos occur through distinct molecular pathways, even though the resulting phenotypes have similarities.

scholarly journals Thyroid hormone induces constitutive keratin gene expression during Xenopus laevis development.

1989 ◽  
Vol 9 (5) ◽  
pp. 1823-1831 ◽  
Author(s):  
P M Mathisen ◽  
L Miller
Keyword(s):  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Constitutive Expression ◽  
High Level Expression ◽  
Keratin Gene ◽  
Explant Cultures ◽  
Extensive Cell ◽  
High Level

We have used in vitro explant cultures of Xenopus laevis skin to investigate the role that the thyroid hormone triiodothyronine (T3) plays in activating the 63-kilodalton (kDa) keratin genes. The activation of these genes in vivo requires two distinct steps, one independent of T3 and one dependent on T3. In this report we have shown that the same two steps are required to fully activate the 63-kDa keratin genes in skin explant cultures, and we have characterized the T3-mediated step in greater detail. Unlike the induction of transcription by T3 or steroid hormones in adult tissues, there was a long latent period of approximately 2 days between the addition of T3 to skin cultures and an increase in concentration of keratin mRNA. While the T3 induction of 63-kDa keratin gene transcription cannot occur until age 48, a short transient exposure of stage 40 skin cultures to T3 resulted in high-level expression of these genes 5 days later, when normal siblings had reached stage 48. This result indicates that T3 induces a stable change in epidermal cells which can be expressed much later, after extensive cell proliferation has occurred in the absence of T3. Once the 63-kDa keratin genes were induced, they were stably expressed, and by the end of metamorphosis T3 had no further effect on their expression. The results suggest that T3 induces constitutive expression of the 63-kDa keratin genes during metamorphosis.

scholarly journals Distinct Tissue-Specific Roles for Thyroid Hormone Receptors β and α1 in Regulation of Type 1 Deiodinase Expression

2001 ◽  
Vol 15 (3) ◽  
pp. 467-475 ◽  
Author(s):  
Lori L. Amma ◽  
Angel Campos-Barros ◽  
Zhendong Wang ◽  
Björn Vennström ◽  
Douglas Forrest
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptors ◽  
Critical Role ◽  
Thyroid Hormone Receptors ◽  
Minor Role ◽  
Tissue Specific ◽  
Mice Liver

Abstract Type 1 deiodinase (D1) metabolizes different forms of thyroid hormones to control levels of T3, the active ligand for thyroid hormone receptors (TR). The D1 gene is itself T3-inducible and here, the regulation of D1 expression by TRα1 and TRβ, which act as T3-dependent transcription factors, was investigated in receptor-deficient mice. Liver and kidney D1 mRNA and activity levels were reduced in TRβ−/− but not TRα1−/− mice. Liver D1 remained weakly T3 inducible in TRβ–/– mice whereas induction was abolished in double mutant TRα1–/–TRβ–/– mice. This indicates that TRβ is primarily responsible for regulating D1 expression whereas TRα1 has only a minor role. In kidney, despite the expression of both TRα1 and TRβ, regulation relied solely on TRβ, thus revealing a marked tissue restriction in TR isotype utilization. Although TRβ and TRα1 mediate similar functions in vitro, these results demonstrate differential roles in regulating D1 expression in vivo and suggest that tissue-specific factors and structural distinctions between TR isotypes contribute to functional specificity. Remarkably, there was an obligatory requirement for a TR, whether TRβ or TRα1, for any detectable D1 expression in liver. This suggests a novel paradigm of gene regulation in which the TR sets both basal expression and the spectrum of induced states. Physiologically, these findings suggest a critical role for TRβ in regulating the thyroid hormone status through D1-mediated metabolism.

scholarly journals Vitamin A5/X, a new food to lipid hormone concept for a nutritional ligand to control RXR-mediated signaling

2020 ◽  
Author(s):  
Wojciech Krezel ◽  
Aurea Rivas ◽  
Monika Szklenar ◽  
Marion Ciancia ◽  
Rosana Alvarez ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Vitamin A ◽  
Retinoic Acid Receptors ◽  
Organic Chemical ◽  
New Class ◽  
Human Food Chain ◽  
Mouse Study ◽  
Β Carotene

Abstract Background: Vitamin A is a family of derivatives synthesized from carotenoids acquired from the diet and can be converted in animals to bioactive forms essential for life. The vitamin A1 (all-trans-retinol / ATROL) and provitamin A1 (all-trans-β,β-carotene / ATBC) are precursors of all-trans-retinoic acid acting as a ligand for the retinoic acid receptors. The contribution of ATROL and ATBC to formation of 9-cis-13,14-dihydroretinoic acid (9CDHRA), the only endogenous retinoid acting as retinoid X receptor ligand remains unknown. Methods: Novel and well know retinoids and carotenoids were synthesized via organic chemical synthesis. Further, novel and well know retinoids / carotenoids were administered to in vitro oligodendrocyte cell culture and to in vivo oral supplemented mice with following HPLC-MS / UV-Vis based metabolomic evaluation of these administered retinoids / carotenoids. In addition, working memory analyses were performed in a mouse study. Results: In this study, we show that ATROL and ATBC are at best only weak and non-selective precursors of 9CDHRA. Instead, we identify 9-cis-13,14-dihydroretinol (9CDHROL) and 9-cis-13,14-dihydro-β,β-carotene (9CDHBC) as novel direct nutritional precursors of 9CDHRA, which are present endogenously in humans and the human food chain matrix. We also propose that the endogenous carotenoid 9-cis-β,β-carotene (9CBC) can also act as weak, indirect precursor of 9CDHRA via hydrogenation to 9CDHBC and further metabolism to 9CDHROL and/or 9CDHRA.Conclusion: In summary, since classical vitamin A1 is not an efficient 9CDHRA precursor, we conclude that this group of molecules constitutes as a new class of vitamin or a new independent member of the vitamin A family, named “Vitamin A5/X”.

scholarly journals Thyroid hormone-stimulated differentiation of primary rib chondrocytes in vitro requires thyroid hormone receptor β

2006 ◽  
Vol 191 (1) ◽  
pp. 221-228 ◽  
Author(s):  
Bénédicte Rabier ◽  
Allan J Williams ◽  
Frederic Mallein-Gerin ◽  
Graham R Williams ◽  
O Chassande
Keyword(s):  
Thyroid Hormone ◽  
Growth Plate ◽  
Hormone Receptors ◽  
Thyroid Hormone Receptor ◽  
Primary Cultures ◽  
Wild Type ◽  
Proliferation And Differentiation ◽  
Thyroid Hormone Receptor Β

The active thyroid hormone, triiodothyronine (T3), binds to thyroid hormone receptors (TR) and plays an essential role in the control of chondrocyte proliferation and differentiation. Hypo- and hyperthyroidism alter the structure of growth plate cartilage and modify chondrocyte gene expression in vivo, whilst TR mutations or deletions in mice result in altered growth plate architecture. Nevertheless, the particular roles of individual TR isoforms in mediating T3 action in chondrocytes have not been studied and are difficult to determine in vivo because of complex cellular and molecular interactions that regulate growth plate maturation. Therefore, we studied the effects of TRα and TRβ on chondrocyte growth and differentiation in primary cultures of neonatal rib chondrocytes isolated from TRα- and TRβ-deficient mice. T3 decreased proliferation but accelerated differentiation of rib chondrocytes from wild-type mice. T3 treatment resulted in similar effects in TRα-deficient chondrocytes, but in TRβ-deficient chondrocytes, all T3 responses were abrogated. Furthermore, T3 increased TRβ1 expression in wild-type and TRα-deficient chondrocytes. These data indicate that T3-stimulated differentiation of primary rib chondrocytes in vitro requires TRβ and suggest that the TRβ1 isoform mediates important T3 actions in mouse rib chondrocytes.

scholarly journals Thyroid hormone receptors are down-regulated in skeletal muscle of patients with non-thyroidal illness syndrome secondary to non-septic shock

2010 ◽  
Vol 163 (5) ◽  
pp. 765-773 ◽  
Author(s):  
J Lado-Abeal ◽  
A Romero ◽  
I Castro-Piedras ◽  
A Rodriguez-Perez ◽  
J Alvarez-Escudero
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Septic Shock ◽  
Thyroid Hormone ◽  
Hormone Receptors ◽  
Serum Samples ◽  
Pathway Activation ◽  
Gene And Protein Expression

AimNon-thyroidal illness syndrome (NTIS) is related to changes in thyroid hormone (TH) physiology. Skeletal muscle (SM) plays a major role in metabolism, and TH regulates SM phenotype and metabolism. We aimed to characterize the SM of non-septic shock NTIS patients in terms of: i) expression of genes and proteins involved in TH metabolism and actions; and ii) NFKB's pathway activation, a responsible factor for some of the phenotypic changes in NTIS. We also investigated whether the patient's serum can induce in vitro the effects observed in vivo.MethodsSerum samples and SM biopsies from 14 patients with non-septic shock NTIS and 11 controls. Gene and protein expression and NFKB1 activation were analyzed by quantitative PCR and immunoblotting. Human SM cell (HSkMC) cultures to investigate the effects of patient's serum on TH action mediators.ResultsPatients with non-septic shock NTIS showed higher levels of pro-inflammatory cytokines than controls. Expression of TRβ (THRB), TRα1 (THRA), and retinoid X receptor γ (RXRG) was decreased in NTIS patients. RXRA gene expression was higher, but its protein was lower in NTIS than controls, suggesting the existence of a post-transcriptional mechanism that down-regulates protein levels. NFKB1 pathway activation was not different between NTIS and control patients. HSkMC incubated with patient's serum increased TH receptor and RXRG gene expression after 48 h.ConclusionsPatients with non-septic shock NTIS showed decreased expression of TH receptors and RXRs, which were not related to increased activation of the NFKB1 pathway. These findings could not be replicated in cultures of HSkMCs incubated in the patient's serum.

scholarly journals Preparation of unoccupied thyroid-hormone receptor

1994 ◽  
Vol 297 (1) ◽  
pp. 75-78 ◽  
Author(s):  
Q Li ◽  
A Inoue
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptors ◽  
Thyroid Hormone Receptor ◽  
Binding Capacity ◽  
Fatty Acyl ◽  
Receptor Complex ◽  
Simple Method ◽  
Sephadex Column

Thyroid hormone (3,5,3′-tri-iodothyronine; T3) regulates gene expression through binding to its specific receptor in the nucleus. In euthyroid animals, roughly half of all receptors are occupied by the hormone. Nuclear extracts thus yield mixtures of occupied and unoccupied receptors. We present here a simple method for transforming occupied receptors into unoccupied ones. In vitro, the T3-receptor complex dissociated in a half-dissociation time exceeding 100 h at 0 degrees C, and at temperatures that accelerated the dissociation the receptor was quickly inactivated. Long-chain-fatty-acyl-CoAs, on the other hand, greatly accelerated the dissociation of T3-receptor complex at 0 degree C. The receptor was extracted from rat liver nuclei, incubated with oleoyl-CoA to release the bound hormone, and passed through a small column of Lipidex, which strongly adsorbed both oleoyl-CoA and the dissociated hormone. The receptor was recovered in the flow-through fraction in its unoccupied form, as seen by the results of DEAE-Sephadex column chromatography and the loss of all previously bound [125I]T3. The maximum T3-binding capacity of the unoccupied receptor was about 1.5-fold that of the untreated sample, and the dissociation constant was unaltered. The results suggest that most nuclear thyroid-hormone receptors occupied by the hormone were transformed into unoccupied ones. From the T3-binding capacity before and after oleoyl-CoA treatment, the in vivo T3 occupancy of the receptor was estimated. The procedure is easy to perform, and the method should be useful for studies of unoccupied receptors.

scholarly journals Heteroarotinoids Inhibit Head and Neck Cancer Cell Lines in Vitro and in Vivo Through Both RAR and RXR Retinoic Acid Receptors

1999 ◽  
Vol 42 (21) ◽  
pp. 4434-4445 ◽  
Author(s):  
David Zacheis ◽  
Arindam Dhar ◽  
Shennan Lu ◽  
Matora M. Madler ◽  
Jozef Klucik ◽  
...  
Keyword(s):  
Head And Neck Cancer ◽  
Retinoic Acid ◽  
Head And Neck ◽  
Cell Lines ◽  
Cancer Cell ◽  
Neck Cancer ◽  
Cancer Cell Lines ◽  
Retinoic Acid Receptors

Thyroid hormone induces constitutive keratin gene expression during Xenopus laevis development

1989 ◽  
Vol 9 (5) ◽  
pp. 1823-1831
Author(s):  
P M Mathisen ◽  
L Miller
Keyword(s):  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Constitutive Expression ◽  
High Level Expression ◽  
Keratin Gene ◽  
Explant Cultures ◽  
Extensive Cell ◽  
High Level

We have used in vitro explant cultures of Xenopus laevis skin to investigate the role that the thyroid hormone triiodothyronine (T3) plays in activating the 63-kilodalton (kDa) keratin genes. The activation of these genes in vivo requires two distinct steps, one independent of T3 and one dependent on T3. In this report we have shown that the same two steps are required to fully activate the 63-kDa keratin genes in skin explant cultures, and we have characterized the T3-mediated step in greater detail. Unlike the induction of transcription by T3 or steroid hormones in adult tissues, there was a long latent period of approximately 2 days between the addition of T3 to skin cultures and an increase in concentration of keratin mRNA. While the T3 induction of 63-kDa keratin gene transcription cannot occur until age 48, a short transient exposure of stage 40 skin cultures to T3 resulted in high-level expression of these genes 5 days later, when normal siblings had reached stage 48. This result indicates that T3 induces a stable change in epidermal cells which can be expressed much later, after extensive cell proliferation has occurred in the absence of T3. Once the 63-kDa keratin genes were induced, they were stably expressed, and by the end of metamorphosis T3 had no further effect on their expression. The results suggest that T3 induces constitutive expression of the 63-kDa keratin genes during metamorphosis.

scholarly journals Do unliganded thyroid hormone receptors have physiological functions?

2003 ◽  
Vol 31 (1) ◽  
pp. 9-20 ◽  
Author(s):  
O Chassande
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptors ◽  
Target Genes ◽  
Thyroid Hormone Receptors ◽  
Intrinsic Activity ◽  
Vertebrate Development ◽  
Transcriptional Responses ◽  
Embryonic And Fetal Development

Thyroid hormone (TH) is required for the development of vertebrates and exerts numerous homeostatic functions in adults. TH acts through nuclear receptors which control the transcription of target genes. Unliganded and liganded thyroid hormone receptors (TRs) have been shown to exert opposite effects on the transcription of target genes in vitro. However, the occurance of an aporeceptor activity in vivo and its potential physiological significance has not been clearly addressed. Several data generated using experimental hypothyroidism and thyrotoxicosis in wild type and TR knockout mice support the notion that apoTRs have an intrinsic activity in several tIssues. ApoTRs, and in particular TRalpha1, are predominant during the early stages of vertebrate development and must be turned into holoTRs for post-natal development to proceed normally. However, the absence of striking alterations of embryonic and fetal development in mice devoid of TRs indicates that apoTRs do not play a fundamental role. During development, as well as in adults, apoTRs rather appears as a system which increases the range of transcriptional responses to moderate variations of T3.

scholarly journals Cells to Systems Screening for Thyroid Hormone Disrupting Chemicals in the Brain

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A484-A485
Author(s):  
J David Furlow ◽  
Brenda J Mengeling
Keyword(s):  
Thyroid Hormone ◽  
Xenopus Laevis ◽  
Environmental Chemicals ◽  
Gh3 Cells ◽  
Luciferase Reporter ◽  
In Vivo Model ◽  
Specific Gene ◽  
Pituitary Cells ◽  
The Brain

Abstract Precisely timed and regulated thyroid hormone (TH) levels are essential for vertebrate development and metabolism. To detect environmental chemicals that disrupt TH action, we developed an integrated luciferase reporter cell line in rat pituitary GH3 cells that is TH responsive through activation of endogenous thyroid hormone receptors (TRs). High throughput screening as part of the Tox21 program identified several non-TH related positive hits as RXR agonists, a supposed “silent” heterodimer partner for TRs. These data showed RXR agonists can affect TR signaling at least in pituitary cells. We extended these results to our sensitive and specific in vivo model for TH action, Xenopus laevis metamorphosis. We previously demonstrated that RXR agonists like organotins and the pharmaceutical bexarotene, strongly potentiate (and RXR antagonists inhibit) TH induced metamorphic programs, at the morphological, cellular (e.g. apoptosis or proliferation), transgenic reporter gene levels, and transcriptomic responses in tadpole tails. We have now extended this analysis to include RNA-Seq experiments over distinct time points in the tadpole brain, a common target of TH in humans and frogs, revealing specific gene sets particularly affected by TH and RXR ligands working in concert. Very few genes were affected by RXR ligands alone. The remarkable overlap between the environmental toxicant tributyltin and the synthetic and specific RXR ligand bexarotene regulated transcriptomes provides strong evidence that they have a common molecular target in multiple tissues. We have also created germline mutations in all RXR family members in Xenopus tropicalis (alpha, beta and gamma), and both copies of the duplicated TR beta gene in Xenopus laevis via genome editing approaches. This will allow us to further investigate TR-RXR heterodimer function across tissues and developmental timeframes, and in response to known and suspected TR and RXR ligands. Our studies revealed an unanticipated degree of TR and RXR ligand interactions in vitro and in vivo, highlighting a surprising role of RXRs as avenues for TH endocrine disruption, including the brain.

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