ABSTRACT
The thyroid gland has the ability to uptake and concentrate iodide, which is a fundamental step in thyroid hormone biosynthesis. Radioiodine has been used as a diagnostic and therapeutic tool for several years. However, the studies related to the mechanisms of iodide transport were only possible after the cloning of the gene that encodes the sodium/iodide symporter (NIS). The studies about the regulation of NIS expression and the possibility of gene therapy with the aim of transferring NIS gene to cells that normally do not express the symporter have also become possible. In the majority of hypofunctioning thyroid nodules, both benign and malignant, NIS gene expression is maintained, but NIS protein is retained in the intracellular compartment. The expression of NIS in non-thyroid tumoral cells in vivo has been possible through the transfer of NIS gene under the control of tissue-specific promoters. Apart from its therapeutic use, NIS has also been used for the localization of metastases by scintigraphy or PET-scan with 124I. In conclusion, NIS gene cloning led to an important development in the field of thyroid pathophysiology, and has also been fundamental to extend the use of radioiodine for the management of non-thyroid tumors.
A glândula tireóide tem capacidade de captar e concentrar iodeto, etapa fundamental na biossíntese dos hormônios tireóideos. O uso de iodo radioativo para fins de diagnóstico e terapia das doenças da tireóide vem sendo feito há muitos anos. Entretanto, somente após a clonagem do gene que codifica o co-transportador de sódio/iodeto (NIS) houve aumento significativo dos estudos relacionados ao mecanismo de transporte de iodeto. Os estudos sobre a regulação da expressão do NIS e a possibilidade de terapia gênica visando à transferência do gene NIS para células que normalmente não expressam esse transportador, foram também viabilizados. Na maior parte dos nódulos tireóideos hipofuncionantes, tanto benignos quanto malignos, a expressão do gene do NIS está presente, mas a proteína NIS fica retida no compartimento intracelular. A transferência do gene usando-se promotores tecido-específicos possibilitou a expressão do NIS em células tumorais não-tireóideas in vivo. Além do seu uso terapêutico, o NIS também vem sendo usado para a localização de metástases tumorais através da cintilografia ou do PET-scan usando-se 124I. Em conclusão, a clonagem do NIS possibilitou enorme avanço na área de fisiopatologia tireóidea e foi também fundamental para estender o uso do radioiodo para tumores não tireóideos.
Subject(s)
Humans , Adenocarcinoma, Follicular/metabolism , Carcinoma, Papillary/metabolism , Iodine/metabolism , Symporters/metabolism , Thyroid Neoplasms/metabolism , Adenocarcinoma, Follicular/therapy , Biological Transport , Cloning, Molecular , Carcinoma, Papillary/therapy , Down-Regulation , Gene Expression , Gene Transfer Techniques , Genetic Therapy , Iodides/metabolism , Iodine Radioisotopes , Iodine Radioisotopes/therapeutic use , Symporters/genetics , Thyroid Neoplasms/therapy , Thyrotropin/physiologyABSTRACT
BACKGROUND: Iodide has been known to control the function and the growth of the thyroid gland, and to be used as a substrate of thyroid hormone. Moreover, it has been suggested that excessive iodide stimulates the thyroid autoimmune responses. To evaluate the effects of iodide on thyrocytes, we investigated cell function and proliferation, or thyroid autoantigen expression after administering iodide to rats or FRTL-5 cells. MEHTODS AND RESULTS: Ten-weeks-old Sprague-Dawley rats were sacrificed after 7 days of NaI treatment. The expressions of thyroid autoantigens were examined by northern blot analysis. Chronic administration of iodide resulted in no effect on TSH receptor (TSHR) and thyroperoxidase (TPO) mRNA expression, while it increased thyroglobulin (TG) and diminished sodium-iodide symporter (NIS) mRNA expression. FRTL-5 cells were also treated with various concentrations of NaI. The generation of cAMP or iodide uptake was decreased, and the cellular growth was also inhibited by iodide. However, the expressions of all thyroid autoantigens (TSHR, TG, TPO, MHC class I and class II) except NIS were unchanged for 72 hours after iodide administration. The expression of NIS was mildly increased after 24 hours. CONCLUSION: Iodide resulted in decreased cell proliferation and cellular function of cAMP generation and iodide uptake. Chronic administration of iodide increased TG and diminished NIS mRNA expression in vivo but not in vitro
Subject(s)
Animals , Rats , Autoantigens , Autoimmunity , Blotting, Northern , Cell Proliferation , Ion Transport , Rats, Sprague-Dawley , Receptors, Thyrotropin , RNA, Messenger , Thyroglobulin , Thyroid GlandABSTRACT
Different human thyroid carcinoma cell lines were treated with all-trans retinoic acid(RA). RA could inhibit cell growth,improve iodide uptake and increase some thyroid specific genes and retinoid acid receptor(RAR)mRNA expressions in FTC-133 cells.However,RA had no effect in C643,HTH74 and XTC. UC1 cells.These findings indicate that different thyroid carcinoma cells display diverse responses to RA.