Thyroid peroxidase gene expression is induced by lipopolysaccharide involving nuclear factor (NF)-κB p65 subunit phosphorylation.
Thyroid peroxidase (TPO), a tissue-specific enzyme expressed in differentiated thyroid follicular cells, is a major antigen that has been linked to autoimmune thyroid disease. We have previously reported the functional expression of the lipopolysaccharide (LPS) receptor Toll-like receptor 4 on thyroid follicular cells. Here we investigated the effect of LPS in TPO expression and analyzed the mechanisms involved. We found a dose-dependent enhancement of TSH-induced TPO expression in response to LPS stimulation. EMSAs demonstrated that LPS treatment increased thyroid transcription factor-1 and -2 binding to the B and Z regions of TPO promoter, respectively. Moreover, LPS increased TSH-stimulated TPO promoter activity. Using bioinformatic analysis, we identified a conserved binding site for transcription nuclear factor-κB (NF-κB) in the TPO promoter. Chemical inhibition of NF-κB signaling and site-directed mutagenesis of the identified κB-cis-acting element abolished LPS stimulation. Furthermore, chromatin immunoprecipitation assays confirmed that TPO constitutes a novel NF-κB p65 subunit target gene in response to LPS. Additionally, our results indicate that p65 phosphorylation of serine 536 constitutes an essential step in the p65-dependent, LPS-induced transcriptional expression of TPO. In conclusion, here we demonstrated that LPS increases TPO expression, suggesting a novel mechanism involved in the regulation of a major thyroid autoantigen. Our results provide new insights into the potential effects of infectious processes on thyroid homeostasis.
Centro de Investigaciones en Bioquímica Clínica e Inmunología, Consejo Nacional de Investigaciones Científicas y Técnicas, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
Magalí
M
Nazar
Juan Pablo
JP
Nicola
María Laura
ML
Vélez
Claudia Gabriela
CG
Pellizas
Ana María
AM
Masini-Repiso
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology / Q000379:methods; D005786:Gene Expression Regulation; D006801:Humans; D007453:Iodide Peroxidase / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051381:Rats; D012694:Serine / Q000737:chemistry; D051197:Toll-Like Receptor 4 / Q000378:metabolism
D008070:Lipopolysaccharides; D016328:NF-kappa B; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D012694:Serine; D007453:Iodide Peroxidase