Project description:Amiodarone reversibly decreases sodium-iodide symporter mRNA expression at therapeutic concentrations and induces antioxidant responses at supraphysiological concentrations in cultured human thyroid follicles Amiodarone, a potent antiarrhythmic agent, is a highly active oxidant, exerting cytotoxic effects on thyrocytes at pharmacological concentrations. Patients receiving amiodarone usually remain euthyroid, but occasionally develop thyroid dysfunction, such as amiodarone-associated hypothyroidism or amiodarone-induced thyrotoxicosis. To elucidate the mechanism by which amiodarone elicits thyroid dysfunction, human thyroid follicles were cultured with TSH and amiodarone at therapeutic (1-2 microM) and pharmacological (10-20microM) concentrations, and the drug-induced effect on whole human gene expression was analyzed by cDNA microarray. Amiodarone at 1-2microM decreased the expression level of the sodium-iodide symporter (NIS) to nearly half, but did not affect genes participating in thyroid hormonogenesis (thyroid peroxidase, thyroglobulin, pendrin, NADPH oxidase). Higher concentrations (10-20 microM) decreased the expression of all these genes, accompanied by increased expression of antioxidant proteins such as heme oxygenase 1 and ferritin. When thyroid follicles obtained from a patient with Graves’ disease who had been treated with amiodarone for 2 months before thyroidectomy were cultured in amiodarone-free medium, TSH-induced thyroid function was intact, suggesting that amiodarone at a maintenance dose did not elicit any cytotoxic effect on thyrocytes. The ultrastructural features of cultured thyroid follicles were compatible with these in vitro findings. These in vitro and ex vivo findings suggest that patients taking maintenance doses of amiodarone usually remain euthyroid, probably due to escape from the Wolff-Chaikoff effect mediated by decreased expression of NIS mRNA. Furthermore, amiodarone is not cytotoxic for thyrocytes at therapeutic concentrations but elicits cytotoxicity through oxidant activity at supra-physiological concentrations. Keywords: Cultured human thyroid follicles

Project description:Graves’ disease is characterized by goiter, palpitation and exophthalmos (Merseburg’s trias). However, a few patients develop exophthalmos even though their thyroid function is normal, a condition known as euthyroid Graves’ disease (EGD). It remains unknown why these patients remain euthyroid, even though they have potent thyroid-stimulating antibody (TSAb). To investigate whether the immunoglobulins (IgGs) obtained from EGD patients elicit thyroid hormone-releasing activity (THRA), thyroid follicles obtained from Graves’ patients were cultured in agarose-coated culture dishes, and 125I incorporated into the thyroid follicles and organic 125I (mainly de novo-synthesized 125I-T3+125I-T4) released into the culture medium by TSH or purified IgGs were determined as thyroid hormone-releasing activity (THRA). This thyroid follicle culture system allows maintenance of the Wolff-Chaikoff effect, and the expression of mRNA for the sodium-iodide symporter is decreased by high concentrations of iodide (10-6-10-4M) and therapeutic concentrations of amiodarone (1-2microM). hTSH elicited THRA most efficiently at 0.4-10 microU/ml, suggesting that thyroid function is controlled within the normal range of TSH concentration (0.4-4.0 microU/ml). All IgGs obtained from hyperthyroid Graves’ patients elicited THRA equivalent to more than 4.6 microU/ml hTSH. IgGs obtained from EGD patients also had potent THRA, whereas IgGs obtained from normal subjects and Graves’ patients in complete remission had no significant THRA. When thyroid follicles from Graves’ thyroid, into which a number of lymphocytes had infiltrated, were used, only slight THRA was elicited by bTSH or Graves’ IgGs, probably due to inflammatory cytokines produced by immunocompetent cells that could not be separated during gentle centrifugation. Indeed, when thyroid follicles were cultured with autologous intrathyroidal lymphocytes, interleukin-2 completely abolished TSH-induced THRA. When thyroid follicles were cultured with inflammatory cytokines (interleukin-1, tumor-necrosis factor-alpha, or interferon-gamma), each cytokine inhibited TSH-induced THRA in a concentration-dependent manner. These cytokines at lower concentrations synergistically and completely inhibited TSH-induced THRA. Microarray analyses of thyroid follicles cultured with IL-1alpha, TNF-alpha, or INF-gamma revealed decreased expression of mRNAs for TSHR, NIS, TPO and thyroglobulin, accompanied by increased expression of mRNAs for chemokines and cytokines. These findings suggest that IgGs obtained from patients with EGD have potent THRA in vitro, whereas in vivo, these IgGs are unable to elicit biological activity in the thyroid gland. Presumably, immunocompetent cells that infiltrate the thyroid gland produce inflammatory cytokines that synergistically inhibit thyroid function. Since a similar phenomenon may occur in the retroorbital tissues, these patients may develop exophthalmos despite having a normal serum level of TSH. This data will be published in Hyperthyroidism: Etiology, Diagnosis and Treatment (editor-in-chief;Dr.Frank Clumbus,Nova Science Publishers, Inc, New York, USA) Experiment Overall Design: One conditioned experiments: control vs. IL-1 alpha 5ng/ml, cultured for 24 hours; control vs. TNF alpha 20ng/ml, cultured for 24 hours; control vs. IFN gamma 1000U/ml, cultured for 48 hours.

Project description:Graves’ disease is characterized by goiter, palpitation and exophthalmos (Merseburg’s trias). However, a few patients develop exophthalmos even though their thyroid function is normal, a condition known as euthyroid Graves’ disease (EGD). It remains unknown why these patients remain euthyroid, even though they have potent thyroid-stimulating antibody (TSAb). To investigate whether the immunoglobulins (IgGs) obtained from EGD patients elicit thyroid hormone-releasing activity (THRA), thyroid follicles obtained from Graves’ patients were cultured in agarose-coated culture dishes, and 125I incorporated into the thyroid follicles and organic 125I (mainly de novo-synthesized 125I-T3+125I-T4) released into the culture medium by TSH or purified IgGs were determined as thyroid hormone-releasing activity (THRA). This thyroid follicle culture system allows maintenance of the Wolff-Chaikoff effect, and the expression of mRNA for the sodium-iodide symporter is decreased by high concentrations of iodide (10-6-10-4M) and therapeutic concentrations of amiodarone (1-2microM). hTSH elicited THRA most efficiently at 0.4-10 microU/ml, suggesting that thyroid function is controlled within the normal range of TSH concentration (0.4-4.0 microU/ml). All IgGs obtained from hyperthyroid Graves’ patients elicited THRA equivalent to more than 4.6 microU/ml hTSH. IgGs obtained from EGD patients also had potent THRA, whereas IgGs obtained from normal subjects and Graves’ patients in complete remission had no significant THRA. When thyroid follicles from Graves’ thyroid, into which a number of lymphocytes had infiltrated, were used, only slight THRA was elicited by bTSH or Graves’ IgGs, probably due to inflammatory cytokines produced by immunocompetent cells that could not be separated during gentle centrifugation. Indeed, when thyroid follicles were cultured with autologous intrathyroidal lymphocytes, interleukin-2 completely abolished TSH-induced THRA. When thyroid follicles were cultured with inflammatory cytokines (interleukin-1, tumor-necrosis factor-alpha, or interferon-gamma), each cytokine inhibited TSH-induced THRA in a concentration-dependent manner. These cytokines at lower concentrations synergistically and completely inhibited TSH-induced THRA. Microarray analyses of thyroid follicles cultured with IL-1alpha, TNF-alpha, or INF-gamma revealed decreased expression of mRNAs for TSHR, NIS, TPO and thyroglobulin, accompanied by increased expression of mRNAs for chemokines and cytokines. These findings suggest that IgGs obtained from patients with EGD have potent THRA in vitro, whereas in vivo, these IgGs are unable to elicit biological activity in the thyroid gland. Presumably, immunocompetent cells that infiltrate the thyroid gland produce inflammatory cytokines that synergistically inhibit thyroid function. Since a similar phenomenon may occur in the retroorbital tissues, these patients may develop exophthalmos despite having a normal serum level of TSH. This data will be published in Hyperthyroidism: Etiology, Diagnosis and Treatment (editor-in-chief;Dr.Frank Clumbus,Nova Science Publishers, Inc, New York, USA)

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