Autoimmune diseases are associated with the presence of multiple autoantigens. This article demonstrates that LPS stimulates Thyroglobulin (TG) one of the major thyroid autoantigens.

View this article in PubMed
1: Endocrinology. 2006 Jul;147(7):3260-75. Epub 2006 Apr 20.

Bacterial lipopolysaccharide stimulates the thyrotropin-dependent thyroglobulin gene expression at the transcriptional level by involving the transcription factors thyroid transcription factor-1 and paired box domain transcription factor 8.

Velez ML, Costamagna E, Kimura ET, Fozzatti L, Pellizas CG, Montesinos MM, Lucero AM, Coleoni AH, Santisteban P, Masini-Repiso AM.

Departamento de Bioquimica Clinica, Facultad de Ciencias Quimicas, Centro de Investigaciones en Bioquimica Clinica e Inmunologia, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Universidad Nacional de Cordoba, 5000 Cordoba, Argentina.

The bacterial lipopolysaccharide (LPS) is a biological activator that induces expression of multiple genes in several cell types. LPS has been proposed as an etiopathogenic agent in autoimmune diseases. However, whether LPS affects the expression of autoantigens has not been explored. Thyroglobulin (TG) is a key protein in thyroid hormonogenesis and one of the major thyroid autoantigens. This study aimed to analyze the action of LPS on TG gene expression in Fisher rat thyroid cell line FRTL-5 thyroid cells. We demonstrate that LPS increases the TSH-induced TG protein and mRNA level. Evidence that the effect of LPS is exerted at the transcriptional level was obtained by transfecting the minimal TG promoter. The C element of the TG promoter, which contains sequences for paired box domain transcription factor 8 (Pax8) and thyroid transcription factor (TTF)-1 binding, is essential for full TG promoter expression under TSH stimulation. The transcriptional activity of a construct containing five tandem repeats of the C site is increased by LPS, indicating a possible involvement of the C site in the LPS-induced TG gene transcription. We demonstrate that the TG promoter mutated at the Pax8 or TTF-1 binding element in the C site does not respond to LPS. In band shift assays, binding of Pax8 and TTF-1 to the C site is increased by LPS. The Pax8 and TTF-1 mRNA and protein levels are augmented by LPS. The half-lives of TG, Pax8, and TTF-1 are increased in endotoxin-treated cells. Our results reveal the ability of LPS to stimulate the expression of TG, a finding of potential pathophysiological implication.

View this article in PubMed
Interleukin-1 production and action in thyroid tissue

Y Kawabe, K Eguchi, C Shimomura, M Mine, T Otsubo, Y Ueki, H Tezuka, H Nakao, A Kawakami and K Migita

First Department of Internal Medicine, Nagasaki University School of Medicine, Japan.

This study was undertaken to determine the effects of interleukin-1 (IL- 1) on human thyroid epithelial cells (thyrocytes) and whether thyrocytes produce IL-1. The supernatants of cultured peripheral blood monocytes stimulated with lipopolysaccharide (LPS) increased [3H]thymidine incorporation into thyrocytes from normal subjects and patients with Grave's disease. The IL-1 levels of cultured supernatants of monocytes were measured by a thymocyte costimulation assay and a solid phase sandwich immunoenzymometric assay. The supernatants of monocyte cultures stimulated with LPS contained significant amounts of IL-1 bioactivity and IL-1 alpha and IL-1 beta immunoactivity. Recombinant IL-1 beta (rIL-1 beta) also stimulated [3H]thymidine incorporation into thyrocytes from normal subjects and patients with Graves' disease, and it increased the proportion of thyrocytes in the S phase of the cell cycle. Furthermore, thyrocytes stimulated with rIL-1 beta for 24 h produced significant amounts of prostaglandin E2. Indomethacin inhibited completely the rIL-1 beta-stimulated prostaglandin E2 production and increased markedly [3H]thymidine incorporation. IL-1-like activity also was detected in the cultured supernatants of lipopolysaccharide (LPS)-stimulated thyrocytes from Graves' and normal thyroid glands, but the amount of IL-1-like activity secreted by thyrocytes was significantly less than that secreted by circulating monocytes. The kinetics of the release of IL-1-like activity by thyrocytes were similar to those of its production by circulating monocytes. Pretreatment of thyrocytes with interferon-gamma failed to enhance the release of IL-1-like activity. Moreover, IL-1 alpha or IL-1 beta immunoreactivity could not be detected in the supernatants of LPS-stimulated thyrocytes, despite the presence of IL-1- like bioactivity. No IL-1 alpha mRNA was detected in unstimulated thyrocytes or thyrocytes stimulated with LPS and phorbol myristate acid. These findings demonstrate that thyrocytes produce an IL-1-like substance(s), but not IL-1, when stimulated by LPS. We conclude that IL- 1 may regulate the proliferation of thyrocytes and that local production of IL-1 by infiltrating monocytes may contribute to the development of goiter in patients with autoimmune thyroid diseases.

Autoinduction of tumor necrosis factor-alpha in FRTL-5 rat thyroid cells.

* Mori K, * Yoshida K, * Komatsu A, * Tani J, * Nakagawa Y, * Hoshikawa S, * Ito S.

Division of Nephrology, Endocrinology and Vascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan. kokimori@mail.tains.tohoku.ac.jp

Tumor necrosis factor-alpha (TNFalpha) may play a role in the development of autoimmune thyroiditis such as Hashimoto's thyroiditis. In the present study, we examined whether TNFalpha induced its own expression in FRTL-5 rat thyroid cells. Lipopolysaccharide (LPS) markedly increased TNFalpha mRNA levels in FRTL-5 cells as assessed by semiquantitative RT-PCR. In addition, LPS-stimulated cells released TNFalpha protein into the culture medium. Similarly, TNFalpha induced its own gene and protein expression in FRTL-5 cells as assessed by RT-PCR and metabolic labeling and immunoprecipitation of TNFalpha. The autoinduction of TNFalpha gene was also observed in TNFalpha-stimulated human thyroid epithelial cells. TNFalpha induction was specific to LPS and TNFalpha since interferon-alpha or amiodarone failed to increase TNFalpha mRNA levels in FRTL-5 cells. Human TNFalpha induced rat TNFalpha gene expression, indicating that type 1 TNF receptor (TNF-R) is involved in the autoinduction. TNFalpha did not increase either type 1 or type 2 TNF-R mRNA levels, suggesting that upregulation of TNF receptors is not involved in the autoinduction of TNFalpha. Although the biological significance of autoinduction of TNFalpha remains unclear, our results suggest that thyroid epithelial cells may participate in the development of autoimmune thyroiditis through production of TNFalpha. Furthermore, inhibition of TNFalpha production in the thyroid may represent a novel approach to mitigating inflammation in autoimmune thyroiditis.

PMID: 16214937 [PubMed - indexed for MEDLINE]