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Robyn L Fisher - One of the best experts on this subject based on the ideXlab platform.
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thyroid organotypic rat and human cultures used to investigate drug effects on thyroid function Hormone Synthesis and release pathways
Toxicology and Applied Pharmacology, 2012Co-Authors: Alison E M Vickers, John R Sinclair, Josh M Rowe, Stephen Morris, Jason Heale, Robyn L FisherAbstract:Drug induced thyroid effects were evaluated in organotypic models utilizing either a rat thyroid lobe or human thyroid slices to compare rodent and human response. An inhibition of thyroid peroxidase (TPO) function led to a perturbation in the expression of key genes in thyroid Hormone Synthesis and release pathways. The clinically used thiourea drugs, methimazole (MMI) and 6-n-propyl-2-thioruacil (PTU), were used to evaluate thyroid drug response in these models. Inhibition of TPO occurred early as shown in rat thyroid lobes (2 h) and was sustained in both rat (24–48 h) and human (24 h) with ≥ 10 μM MMI. Thyroid from rats treated with single doses of MMI (30–1000 mg/kg) exhibited sustained TPO inhibition at 48 h. The MMI in vivo thyroid concentrations were comparable to the culture concentrations (∼ 15–84 μM), thus demonstrating a close correlation between in vivo and ex vivo thyroid effects. A compensatory response to TPO inhibition was demonstrated in the rat thyroid lobe with significant up-regulation of genes involved in the pathway of thyroid Hormone Synthesis (Tpo, Dio1, Slc5a5, Tg, Tshr) and the megalin release pathway (Lrp2) by 24 h with MMI (≥ 10 μM) and PTU (100 μM). Similarly, thyroid from the rat inmore » vivo study exhibited an up-regulation of Dio1, Slc5a5, Lrp2, and Tshr. In human thyroid slices, there were few gene expression changes (Slc5a5, ∼ 2-fold) and only at higher MMI concentrations (≥ 1500 μM, 24 h). Extended exposure (48 h) resulted in up-regulation of Tpo, Dio1 and Lrp2, along with Slc5a5 and Tshr. In summary, TPO was inhibited by similar MMI concentrations in rat and human tissue, however an increased sensitivity to drug treatment in rat is indicated by the up-regulation of thyroid Hormone Synthesis and release gene pathways at concentrations found not to affect human tissue. -- Highlights: ► Novel model of rat thyroid or human thyroid slices to evaluate pathways of injury. ► TPO inhibition by MMI or PTU altered Hormone Synthesis and release genes. ► Rat thyroid was more sensitive to the drug effects than human tissue.« less
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Thyroid organotypic rat and human cultures used to investigate drug effects on thyroid function, Hormone Synthesis and release pathways.
Toxicology and applied pharmacology, 2012Co-Authors: Alison E M Vickers, John R Sinclair, Josh M Rowe, Stephen Morris, Jason Heale, Robyn L FisherAbstract:Drug induced thyroid effects were evaluated in organotypic models utilizing either a rat thyroid lobe or human thyroid slices to compare rodent and human response. An inhibition of thyroid peroxidase (TPO) function led to a perturbation in the expression of key genes in thyroid Hormone Synthesis and release pathways. The clinically used thiourea drugs, methimazole (MMI) and 6-n-propyl-2-thioruacil (PTU), were used to evaluate thyroid drug response in these models. Inhibition of TPO occurred early as shown in rat thyroid lobes (2 h) and was sustained in both rat (24-48 h) and human (24 h) with ≥ 10 μM MMI. Thyroid from rats treated with single doses of MMI (30-1000 mg/kg) exhibited sustained TPO inhibition at 48 h. The MMI in vivo thyroid concentrations were comparable to the culture concentrations (~15-84 μM), thus demonstrating a close correlation between in vivo and ex vivo thyroid effects. A compensatory response to TPO inhibition was demonstrated in the rat thyroid lobe with significant up-regulation of genes involved in the pathway of thyroid Hormone Synthesis (Tpo, Dio1, Slc5a5, Tg, Tshr) and the megalin release pathway (Lrp2) by 24h with MMI (≥ 10 μM) and PTU (100 μM). Similarly, thyroid from the rat in vivo study exhibited an up-regulation of Dio1, Slc5a5, Lrp2, and Tshr. In human thyroid slices, there were few gene expression changes (Slc5a5, ~2-fold) and only at higher MMI concentrations (≥ 1500 μM, 24h). Extended exposure (48 h) resulted in up-regulation of Tpo, Dio1 and Lrp2, along with Slc5a5 and Tshr. In summary, TPO was inhibited by similar MMI concentrations in rat and human tissue, however an increased sensitivity to drug treatment in rat is indicated by the up-regulation of thyroid Hormone Synthesis and release gene pathways at concentrations found not to affect human tissue.
Bernard Mallet - One of the best experts on this subject based on the ideXlab platform.
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production of immunoreactive thyroglobulin c terminal fragments during thyroid Hormone Synthesis
Endocrinology, 2000Co-Authors: Christine Duthoit, Bernard Mallet, Valerie Estienne, Joseemartine Durandgorde, Frederic Delom, Pierre CarayonAbstract:Here, we studied the fragmentation of the prothyroid Hormone, thyroglobulin (Tg), which occurs during thyroid Hormone Synthesis, a process which involves iodide, thyroperoxidase, and the H2O2-generating system, consisting of glucose and glucose oxidase. Various peptides were found to be immunoreactive to autoantibodies to Tg from patients and monoclonal antibodies directed against the immunodominant region of Tg. The smallest peptide (40 kDa) bore thyroid Hormones and was identified at the C-terminal end of the Tg molecule, which shows homologies with acetylcholinesterase. Similar peptides were obtained by performing metal-mediated oxidation of Tg via a Fenton reaction. It was concluded that the oxidative stress induced during Hormone Synthesis generates free radicals, which, in turn, cleave Tg into immunoreactive peptides.
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dityrosine bridge formation and thyroid Hormone Synthesis are tightly linked and are both dependent on n glycans
FEBS Letters, 1996Co-Authors: Nathalie Baudry, Pierrejean Lejeune, Liliane Vinet, Pierre Carayon, P Niccoli, Bernard MalletAbstract:Formation of dityrosine bridges is a ubiquitous process mainly attributed to oxidative stress leading to protein degradation and cellular damages. Here we show that dityrosine formation is involved in a physiological process, thyroid Hormone Synthesis, and is strictly dependent on structural characteristics, namely N-glycans, presented by the protein acting as the prothyroid Hormone. We used two isoforms of the N-terminal thyroid Hormone forming domain (NTD) of human thyroglobulin: one without N-glycan (19 kDa isoform) and the other with high mannose type structures (25 kDa isoform). Both isoforms were able to form iodotyrosines after in vitro iodination. However, iodotyrosine coupling to form thyroxine did not occur with the unglycosylated 19 kDa NTD. In contrast, the 25 kDa isoform formed thyroxine. Strikingly, thyroxine Synthesis was accompanied by dimerization of the 25 kDa isoform and formation of a dityrosine bridge; none of this was observed with the 19 kDa isoform. Taken as a whole, our results indicate that dimerization through dityrosine bridging accompanies and could have a role in thyroid Hormone Synthesis.
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n glycans modulate in vivo and in vitro thyroid Hormone Synthesis study at the n terminal domain of thyroglobulin
Journal of Biological Chemistry, 1995Co-Authors: Bernard Mallet, Pierrejean Lejeune, Pierre Carayon, P Niccoli, Nathalie Baudry, Jean-louis FrancAbstract:Abstract Thyroglobulin (Tg) is the substrate for thyroid Hormone bioSynthesis, which requires tyrosine iodination and iodotyrosine coupling and occurs at the apical membrane of the thyrocytes. Tg glycoconjugates have been shown to play a major role in Tg routing through cellular compartments and recycling after endocytosis. Here we show that glycoconjugates also play a direct role in hormonoSynthesis. The N-terminal domain (NTD; Asn1-Met) of human Tg, which bears the preferential hormonogenic site, brings two N-glycans (Asn and Asn). NTD preparations were purified from Tg with low and mild iodine content in vivo and from poorly iodinated Tg after in vitro iodination and coupling. NTD separated from poorly iodinated Tg was also submitted to iodination and coupling after desialylation and deglycosylation. The various NTD isoforms were analyzed for their N-glycan structures and Hormone contents. Our results show that 1) in vivo as well as in vitro unglycosylated isoforms did not synthesize Hormones, whereas fully or partially (at Asn) glycosylated isoforms did; 2) high mannose type structures enhanced the Hormone content; and 3) desialylation did not affect in vitro Hormone Synthesis. Evidence of a direct involvement in hormonoSynthesis adds to the role of N-glycans in Tg function and opens the way to new mechanisms for regulation (e.g. TSH modulation of N-glycan) or alteration (e.g. Asn mutation) of thyroid Hormone Synthesis.
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N-Glycans Modulate in Vivo and in Vitro Thyroid Hormone Synthesis
Journal of Biological Chemistry, 1995Co-Authors: Bernard Mallet, Pierrejean Lejeune, Pierre Carayon, P Niccoli, Nathalie Baudry, Jean-louis FrancAbstract:Thyroglobulin (Tg) is the substrate for thyroid Hormone bioSynthesis, which requires tyrosine iodination and iodotyrosine coupling and occurs at the apical membrane of the thyrocytes. Tg glycoconjugates have been shown to play a major role in Tg routing through cellular compartments and recycling after endocytosis. Here we show that glycoconjugates also play a direct role in hormonoSynthesis. The N-terminal domain (NTD; Asn1-Met171) of human Tg, which bears the preferential hormonogenic site, brings two N-glycans (Asn57 and Asn91). NTD preparations were purified from Tg with low and mild iodine content in vivo and from poorly iodinated Tg after in vitro iodination and coupling. NTD separated from poorly iodinated Tg was also submitted to iodination and coupling after desialylation and deglycosylation. The various NTD isoforms were analyzed for their N-glycan structures and Hormone contents. Our results show that 1) in vivo as well as in vitro unglycosylated isoforms did not synthesize Hormones, whereas fully or partially (at Asn91) glycosylated isoforms did; 2) high mannose type structures enhanced the Hormone content; and 3) desialylation did not affect in vitro Hormone Synthesis. Evidence of a direct involvement in hormonoSynthesis adds to the role of N-glycans in Tg function and opens the way to new mechanisms for regulation (e.g. TSH modulation of N-glycan) or alteration (e.g. Asn91 mutation) of thyroid Hormone Synthesis.
Pierre Carayon - One of the best experts on this subject based on the ideXlab platform.
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production of immunoreactive thyroglobulin c terminal fragments during thyroid Hormone Synthesis
Endocrinology, 2000Co-Authors: Christine Duthoit, Bernard Mallet, Valerie Estienne, Joseemartine Durandgorde, Frederic Delom, Pierre CarayonAbstract:Here, we studied the fragmentation of the prothyroid Hormone, thyroglobulin (Tg), which occurs during thyroid Hormone Synthesis, a process which involves iodide, thyroperoxidase, and the H2O2-generating system, consisting of glucose and glucose oxidase. Various peptides were found to be immunoreactive to autoantibodies to Tg from patients and monoclonal antibodies directed against the immunodominant region of Tg. The smallest peptide (40 kDa) bore thyroid Hormones and was identified at the C-terminal end of the Tg molecule, which shows homologies with acetylcholinesterase. Similar peptides were obtained by performing metal-mediated oxidation of Tg via a Fenton reaction. It was concluded that the oxidative stress induced during Hormone Synthesis generates free radicals, which, in turn, cleave Tg into immunoreactive peptides.
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dityrosine bridge formation and thyroid Hormone Synthesis are tightly linked and are both dependent on n glycans
FEBS Letters, 1996Co-Authors: Nathalie Baudry, Pierrejean Lejeune, Liliane Vinet, Pierre Carayon, P Niccoli, Bernard MalletAbstract:Formation of dityrosine bridges is a ubiquitous process mainly attributed to oxidative stress leading to protein degradation and cellular damages. Here we show that dityrosine formation is involved in a physiological process, thyroid Hormone Synthesis, and is strictly dependent on structural characteristics, namely N-glycans, presented by the protein acting as the prothyroid Hormone. We used two isoforms of the N-terminal thyroid Hormone forming domain (NTD) of human thyroglobulin: one without N-glycan (19 kDa isoform) and the other with high mannose type structures (25 kDa isoform). Both isoforms were able to form iodotyrosines after in vitro iodination. However, iodotyrosine coupling to form thyroxine did not occur with the unglycosylated 19 kDa NTD. In contrast, the 25 kDa isoform formed thyroxine. Strikingly, thyroxine Synthesis was accompanied by dimerization of the 25 kDa isoform and formation of a dityrosine bridge; none of this was observed with the 19 kDa isoform. Taken as a whole, our results indicate that dimerization through dityrosine bridging accompanies and could have a role in thyroid Hormone Synthesis.
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n glycans modulate in vivo and in vitro thyroid Hormone Synthesis study at the n terminal domain of thyroglobulin
Journal of Biological Chemistry, 1995Co-Authors: Bernard Mallet, Pierrejean Lejeune, Pierre Carayon, P Niccoli, Nathalie Baudry, Jean-louis FrancAbstract:Abstract Thyroglobulin (Tg) is the substrate for thyroid Hormone bioSynthesis, which requires tyrosine iodination and iodotyrosine coupling and occurs at the apical membrane of the thyrocytes. Tg glycoconjugates have been shown to play a major role in Tg routing through cellular compartments and recycling after endocytosis. Here we show that glycoconjugates also play a direct role in hormonoSynthesis. The N-terminal domain (NTD; Asn1-Met) of human Tg, which bears the preferential hormonogenic site, brings two N-glycans (Asn and Asn). NTD preparations were purified from Tg with low and mild iodine content in vivo and from poorly iodinated Tg after in vitro iodination and coupling. NTD separated from poorly iodinated Tg was also submitted to iodination and coupling after desialylation and deglycosylation. The various NTD isoforms were analyzed for their N-glycan structures and Hormone contents. Our results show that 1) in vivo as well as in vitro unglycosylated isoforms did not synthesize Hormones, whereas fully or partially (at Asn) glycosylated isoforms did; 2) high mannose type structures enhanced the Hormone content; and 3) desialylation did not affect in vitro Hormone Synthesis. Evidence of a direct involvement in hormonoSynthesis adds to the role of N-glycans in Tg function and opens the way to new mechanisms for regulation (e.g. TSH modulation of N-glycan) or alteration (e.g. Asn mutation) of thyroid Hormone Synthesis.
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N-Glycans Modulate in Vivo and in Vitro Thyroid Hormone Synthesis
Journal of Biological Chemistry, 1995Co-Authors: Bernard Mallet, Pierrejean Lejeune, Pierre Carayon, P Niccoli, Nathalie Baudry, Jean-louis FrancAbstract:Thyroglobulin (Tg) is the substrate for thyroid Hormone bioSynthesis, which requires tyrosine iodination and iodotyrosine coupling and occurs at the apical membrane of the thyrocytes. Tg glycoconjugates have been shown to play a major role in Tg routing through cellular compartments and recycling after endocytosis. Here we show that glycoconjugates also play a direct role in hormonoSynthesis. The N-terminal domain (NTD; Asn1-Met171) of human Tg, which bears the preferential hormonogenic site, brings two N-glycans (Asn57 and Asn91). NTD preparations were purified from Tg with low and mild iodine content in vivo and from poorly iodinated Tg after in vitro iodination and coupling. NTD separated from poorly iodinated Tg was also submitted to iodination and coupling after desialylation and deglycosylation. The various NTD isoforms were analyzed for their N-glycan structures and Hormone contents. Our results show that 1) in vivo as well as in vitro unglycosylated isoforms did not synthesize Hormones, whereas fully or partially (at Asn91) glycosylated isoforms did; 2) high mannose type structures enhanced the Hormone content; and 3) desialylation did not affect in vitro Hormone Synthesis. Evidence of a direct involvement in hormonoSynthesis adds to the role of N-glycans in Tg function and opens the way to new mechanisms for regulation (e.g. TSH modulation of N-glycan) or alteration (e.g. Asn91 mutation) of thyroid Hormone Synthesis.
Alison E M Vickers - One of the best experts on this subject based on the ideXlab platform.
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thyroid organotypic rat and human cultures used to investigate drug effects on thyroid function Hormone Synthesis and release pathways
Toxicology and Applied Pharmacology, 2012Co-Authors: Alison E M Vickers, John R Sinclair, Josh M Rowe, Stephen Morris, Jason Heale, Robyn L FisherAbstract:Drug induced thyroid effects were evaluated in organotypic models utilizing either a rat thyroid lobe or human thyroid slices to compare rodent and human response. An inhibition of thyroid peroxidase (TPO) function led to a perturbation in the expression of key genes in thyroid Hormone Synthesis and release pathways. The clinically used thiourea drugs, methimazole (MMI) and 6-n-propyl-2-thioruacil (PTU), were used to evaluate thyroid drug response in these models. Inhibition of TPO occurred early as shown in rat thyroid lobes (2 h) and was sustained in both rat (24–48 h) and human (24 h) with ≥ 10 μM MMI. Thyroid from rats treated with single doses of MMI (30–1000 mg/kg) exhibited sustained TPO inhibition at 48 h. The MMI in vivo thyroid concentrations were comparable to the culture concentrations (∼ 15–84 μM), thus demonstrating a close correlation between in vivo and ex vivo thyroid effects. A compensatory response to TPO inhibition was demonstrated in the rat thyroid lobe with significant up-regulation of genes involved in the pathway of thyroid Hormone Synthesis (Tpo, Dio1, Slc5a5, Tg, Tshr) and the megalin release pathway (Lrp2) by 24 h with MMI (≥ 10 μM) and PTU (100 μM). Similarly, thyroid from the rat inmore » vivo study exhibited an up-regulation of Dio1, Slc5a5, Lrp2, and Tshr. In human thyroid slices, there were few gene expression changes (Slc5a5, ∼ 2-fold) and only at higher MMI concentrations (≥ 1500 μM, 24 h). Extended exposure (48 h) resulted in up-regulation of Tpo, Dio1 and Lrp2, along with Slc5a5 and Tshr. In summary, TPO was inhibited by similar MMI concentrations in rat and human tissue, however an increased sensitivity to drug treatment in rat is indicated by the up-regulation of thyroid Hormone Synthesis and release gene pathways at concentrations found not to affect human tissue. -- Highlights: ► Novel model of rat thyroid or human thyroid slices to evaluate pathways of injury. ► TPO inhibition by MMI or PTU altered Hormone Synthesis and release genes. ► Rat thyroid was more sensitive to the drug effects than human tissue.« less
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Thyroid organotypic rat and human cultures used to investigate drug effects on thyroid function, Hormone Synthesis and release pathways.
Toxicology and applied pharmacology, 2012Co-Authors: Alison E M Vickers, John R Sinclair, Josh M Rowe, Stephen Morris, Jason Heale, Robyn L FisherAbstract:Drug induced thyroid effects were evaluated in organotypic models utilizing either a rat thyroid lobe or human thyroid slices to compare rodent and human response. An inhibition of thyroid peroxidase (TPO) function led to a perturbation in the expression of key genes in thyroid Hormone Synthesis and release pathways. The clinically used thiourea drugs, methimazole (MMI) and 6-n-propyl-2-thioruacil (PTU), were used to evaluate thyroid drug response in these models. Inhibition of TPO occurred early as shown in rat thyroid lobes (2 h) and was sustained in both rat (24-48 h) and human (24 h) with ≥ 10 μM MMI. Thyroid from rats treated with single doses of MMI (30-1000 mg/kg) exhibited sustained TPO inhibition at 48 h. The MMI in vivo thyroid concentrations were comparable to the culture concentrations (~15-84 μM), thus demonstrating a close correlation between in vivo and ex vivo thyroid effects. A compensatory response to TPO inhibition was demonstrated in the rat thyroid lobe with significant up-regulation of genes involved in the pathway of thyroid Hormone Synthesis (Tpo, Dio1, Slc5a5, Tg, Tshr) and the megalin release pathway (Lrp2) by 24h with MMI (≥ 10 μM) and PTU (100 μM). Similarly, thyroid from the rat in vivo study exhibited an up-regulation of Dio1, Slc5a5, Lrp2, and Tshr. In human thyroid slices, there were few gene expression changes (Slc5a5, ~2-fold) and only at higher MMI concentrations (≥ 1500 μM, 24h). Extended exposure (48 h) resulted in up-regulation of Tpo, Dio1 and Lrp2, along with Slc5a5 and Tshr. In summary, TPO was inhibited by similar MMI concentrations in rat and human tissue, however an increased sensitivity to drug treatment in rat is indicated by the up-regulation of thyroid Hormone Synthesis and release gene pathways at concentrations found not to affect human tissue.
G J Beckett - One of the best experts on this subject based on the ideXlab platform.
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thyroidal extracellular glutathione peroxidase a potential regulator of thyroid Hormone Synthesis
Biochemical Journal, 1995Co-Authors: A F Howie, John R. Arthur, Björn Åkesson, S W Walker, G J BeckettAbstract:Human thyrocytes were found to synthesize and secrete the selenoenzyme extracellular glutathione peroxidase (E-GPX), a process which was controlled by the Ca2+/phosphoinositol second-messenger cascade. The potential involvement of thyroidal E-GPX in the regulation of thyroid-Hormone Synthesis and in the protection of the thyrocyte from peroxidative damage is discussed.