Zeöld Anikó, Doleschall Márton, Haffner Michael C, Capelo Luciane P, Menyhért Judit, Liposits Zsolt, da Silva Wagner S, Bianco Antonio C, Kacskovics Imre, Fekete Csaba, Gereben Balázs
Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Faculty of Information Technology, Péter Pázmány Catholic University, Budapest H-1083, Hungary.
Endocrinology. 2006 Sep;147(9):4419-29. doi: 10.1210/en.2005-1608. Epub 2006 May 25.
Type 2 iodothyronine deiodinase (D2) activates T4 by deiodination to T3, a process being the source of most T3 present in the brain. In the mediobasal hypothalamus, expression of the dio2 gene is potently activated by administration of bacterial lipopolysaccharide (LPS), which in turn mediates the modifications in thyroid homeostasis typically observed in patients with nonthyroidal illness syndrome. Here we show that LPS-induced D2 expression is also observed in human MSTO-211H cells that endogenously express D2. Exposure to LPS rapidly doubled D2 activity by a mechanism that was partially blocked by the nuclear factor-B (NF-B) inhibitor sulfasalazine. Next, the human dio2 5'-flanking region promoter assay was used in HC11 cells and the p65/NF-kappa B responsiveness mapped to the 3' approximately 600-bp region of hdio2 5'-flanking region, with an approximately 15-fold induction. Semiquantitative EMSA identified the strongest NF-B binding sites at the positions -683 bp (called no. 2) and -198 bp (no. 5) 5' to the transcriptional starting site. Despite the very similar NF-kappa B binding affinity of these two sites, site-directed mutagenesis and promoter assay indicated that only site no. 5 possessed transactivation potency in the presence of the p65 subunit of NF-kappa B. Other cytokine mediators such as signal transducer and activator of transcription-3 (STAT3) or signal transducer and activator of transcription-5 (STAT5) did not induce transcription of the dio2 gene. Our results indicate that inflammatory signals regulate D2 expression predominantly via the NF-kappa B pathway in a direct transcriptional manner and could contribute to the changes in thyroid economy observed in nonthyroidal illness syndrome during infection.
2型碘甲状腺原氨酸脱碘酶（D2）通过将T4脱碘转化为T3来激活T4，这一过程是大脑中大多数T3的来源。在中基底下丘脑，给予细菌脂多糖（LPS）可有效激活dio2基因的表达，进而介导非甲状腺疾病综合征患者中常见的甲状腺内环境稳定的改变。在此我们表明，在内源性表达D2的人MSTO-211H细胞中也观察到LPS诱导的D2表达。暴露于LPS可通过一种机制使D2活性迅速加倍，该机制被核因子-κB（NF-κB）抑制剂柳氮磺胺吡啶部分阻断。接下来，在HC11细胞中进行了人dio2 5'-侧翼区启动子分析，并将p65/NF-κB反应性定位到hdio2 5'-侧翼区的3'端约600 bp区域，诱导倍数约为15倍。半定量电泳迁移率变动分析确定了转录起始位点5'端-683 bp（称为2号位点）和-198 bp（5号位点）处最强的NF-κB结合位点。尽管这两个位点的NF-κB结合亲和力非常相似，但定点诱变和启动子分析表明，在存在NF-κB的p65亚基时，只有5号位点具有反式激活能力。其他细胞因子介质，如信号转导和转录激活因子3（STAT3）或信号转导和转录激活因子5（STAT5），不会诱导dio2基因的转录。我们的结果表明，炎症信号主要通过NF-κB途径以直接转录的方式调节D2表达，并可能导致感染期间非甲状腺疾病综合征中观察到的甲状腺功能变化。
