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.
Endocrinology. 2012 Dec;153(12):6114-25. doi: 10.1210/en.2012-1567. Epub 2012 Oct 12.
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.
甲状腺过氧化物酶（TPO）是一种在分化的甲状腺滤泡细胞中表达的组织特异性酶，是与自身免疫性甲状腺疾病相关的主要抗原。我们之前曾报道过甲状腺滤泡细胞上脂多糖（LPS）受体 Toll 样受体 4 的功能表达。在这里，我们研究了 LPS 对 TPO 表达的影响，并分析了涉及的机制。我们发现 LPS 刺激可剂量依赖性增强 TSH 诱导的 TPO 表达。EMSA 表明 LPS 处理分别增加了甲状腺转录因子-1 和 -2 与 TPO 启动子 B 和 Z 区的结合。此外，LPS 增加了 TSH 刺激的 TPO 启动子活性。通过生物信息学分析，我们在 TPO 启动子中鉴定出了一个保守的转录核因子-κB（NF-κB）结合位点。NF-κB 信号的化学抑制和鉴定出的κB 顺式作用元件的定点突变消除了 LPS 刺激。此外，染色质免疫沉淀分析证实 TPO 是 LPS 刺激后 NF-κB p65 亚基的一个新的靶基因。此外，我们的结果表明，p65 丝氨酸 536 的磷酸化是 p65 依赖性、LPS 诱导的 TPO 转录表达的一个必要步骤。总之，我们证明了 LPS 可增加 TPO 的表达，提示了一种调节主要甲状腺自身抗原的新机制。我们的研究结果为感染过程对甲状腺内稳态的潜在影响提供了新的见解。
