Overexpression of Interleukin-4 in the Thyroid of Transgenic Mice Upregulates the Expression of Duox1 and the Anion Transporter Pendrin.
The dual oxidases (Duox) are involved in hydrogen peroxide generation, which is essential for thyroid hormone synthesis, and therefore they are markers of thyroid function. During inflammation, cytokines upregulate DUOX gene expression in the airway and the intestine, suggesting a role for these proteins in innate immunity. It was previously demonstrated that interleukin-4 (IL-4) upregulates DUOX gene expression in thyrocytes. Although the role of IL-4 in autoimmune thyroid diseases has been studied extensively, the effects of IL-4 on thyroid physiology remain largely unknown. Therefore, a new animal model was generated to study the impact of IL-4 on thyroid function.



Transgenic (Thyr-IL-4) mice with thyroid-targeted expression of murine IL-4 were generated. Transgene expression was verified at the mRNA and protein level in thyroid tissues and primary cultures. The phenotype of the Thyr-IL-4 animals was characterized by measuring serum thyroxine (T4) and thyrotropin levels and performing thyroid morphometric analysis, immunohistochemistry, whole transcriptome sequencing, quantitative reverse transcription polymerase chain reaction, and ex vivo thyroid function assays.



Thyrocytes from two Thyr-IL-4 mouse lines (#30 and #52) expressed IL-4, which was secreted into the extracellular space. Although 10-month-old transgenic animals had T4 and thyrotropin serum levels in the normal range, they had altered thyroid follicular structure with enlarged follicles composed of elongated thyrocytes containing numerous endocytic vesicles. These follicles were positive for T4 staining the colloid, indicating their capacity to produce thyroid hormones. RNA profiling of Thyr-IL-4 thyroid samples revealed modulation of multiple genes involved in inflammation, while no major leukocyte infiltration could be detected. Upregulated expression of Duox1, Duoxa1, and the pendrin anion exchanger gene (Slc26a4) was detected. In contrast, the iodide symporter gene Slc5a5 was markedly downregulated resulting in impaired iodide uptake and reduced thyroid hormone levels in transgenic thyroid tissue. Hydrogen peroxide production was increased in Thyr-IL-4 thyroid tissue compared with wild-type animals, but no significant oxidative stress could be detected.



This is the first study to show that ectopic expression of IL-4 in thyroid tissue upregulates Duox1/Duoxa1 and Slc26a4 expression in the thyroid. The present data demonstrate that IL-4 could affect thyroid morphology and function, mainly by downregulating Slc5a5 expression, while maintaining a normal euthyroid phenotype.
1 Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université libre de Bruxelles (ULB) , Brussels, Belgium .
Zineb
Z
Eskalli
2 Institut De Duve, Université Catholique de Louvain (UCL) , Brussels, Belgium .
Younes
Y
Achouri
3 Laboratory of Image, Signal processing and Acoustics-Brussels School of Engineering, Université libre de Bruxelles (ULB) , Brussels, Belgium .
Stephan
S
Hahn
4 Pôle de Morphologie (MORF), Université Catholique de Louvain (UCL) , Brussels, Belgium .
Marie-Christine
MC
Many
4 Pôle de Morphologie (MORF), Université Catholique de Louvain (UCL) , Brussels, Belgium .
Julie
J
Craps
5 Department of Medicine, University of Chicago , Chicago, Illinois.
Samuel
S
Refetoff
5 Department of Medicine, University of Chicago , Chicago, Illinois.
Xiao-Hui
XH
Liao
1 Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université libre de Bruxelles (ULB) , Brussels, Belgium .
Jacques E
JE
Dumont
1 Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université libre de Bruxelles (ULB) , Brussels, Belgium .
Jacqueline
J
Van Sande
6 Department of Endocrinology, ULB-Hôpital Erasme , Brussels, Belgium .
Bernard
B
Corvilain
1 Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université libre de Bruxelles (ULB) , Brussels, Belgium .
Françoise
F
Miot
1 Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université libre de Bruxelles (ULB) , Brussels, Belgium .
Xavier
X
De Deken
D065567:Absorption, Physiological; D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D000074623:Dual Oxidases / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D006861:Hydrogen Peroxide / Q000378:metabolism; D015847:Interleukin-4 / Q000235:genetics / Q000378:metabolism*; D007454:Iodides / Q000378:metabolism; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000076988:Sulfate Transporters; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D013974:Thyroxine / Q000097:blood / Q000378:metabolism; D015854:Up-Regulation; D000099209:Sodium-Iodide Symporters
D027321:Anion Transport Proteins; D000074623:Dual Oxidases; D006861:Hydrogen Peroxide; D015847:Interleukin-4; D007454:Iodides; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D000076988:Sulfate Transporters; D027981:Symporters; D013972:Thyrotropin; D013974:Thyroxine; D000099209:Sodium-Iodide Symporters; C560186:DUOXA1 protein, mouse; C494849:Slc26a4 protein, mouse; C519130:Duox1 protein, mouse