Zhang Xiaowen, Jiang Yaqiu, Han Wenqing, Liu Aihua, Xie Xiaochen, Han Cheng, Fan Chenling, Wang Hong, Zhang Hongmei, Ding Shuangning, Shan Zhongyan, Teng Weiping
The Endocrine Institute and the Liaoning Provincial Key Laboratory of Endocrine Diseases, Department of Endocrinology and Metabolism, The First Hospital of China Medical University, No.155, North Nanjing Street, Heping District, Shenyang, China.
Biol Trace Elem Res. 2016 Dec;174(2):377-386. doi: 10.1007/s12011-016-0723-2. Epub 2016 May 7.
The purpose of this study is to determine the effect of prolonged iodine overdose on type 2 iodothyronine deiodinase (D2) ubiquitination-related enzymes. Male Wistar rats were fed different doses of iodine and were then euthanized at the 4, 8, 12, or 24 weeks (4w, 8w, 12w, or 24w) after iodine administration. Urinary iodine concentration (UIC), thyroid-stimulating hormone (TSH), total thyroxine (TT4), and total triiodothyronine (TT3) were determined. Real-time quantitative RT-PCR and Western blot were used to measure mRNA and protein expression levels of pituitary D2 as well as two D2-specific ubiquitin ligases [WD repeat and SOCS box-containing protein 1 (WSB-1), membrane-associated ring finger (C3HC4) 6 (MARCH6 or TEB4)] and two D2-specific deubiquitinating enzymes [ubiquitin-specific peptidase 20 (USP20) and ubiquitin-specific peptidase 33 (USP33)]. The mRNA and protein expression levels of USP19, a TEB4-specific deubiquitinating enzyme, were also measured. Prolonged high iodine intake significantly increased TSH expression. At 12w, TSH was 1.57-, 1.44-, and 2.11-fold of NI group in 6HI, 10HI, and 50HI groups, respectively. At 24w, TSH had increased to 2.11-fold in the 50HI group. The pituitary D2 protein level decreased at 12w and 24w; though the mRNA level did not change. Prolonged iodine intake increased mRNA and protein expression levels of pituitary WSB-1 and TEB4. High iodine intake had no discernible effects on USP20. Temporary increases in USP33 and USP19 mRNA levels were observed. The enzymes related to D2 ubiquitination change with prolonged high iodine intake. Increased D2 ubiquitination suppresses the activity of D2, causing a decrease in negative feedback of the hypothalamic-pituitary-thyroid axis.
本研究的目的是确定长期碘过量对2型碘甲状腺原氨酸脱碘酶（D2）泛素化相关酶的影响。将雄性Wistar大鼠喂食不同剂量的碘，然后在给予碘后的第4、8、12或24周（4周、8周、12周或24周）实施安乐死。测定尿碘浓度（UIC）、促甲状腺激素（TSH）、总甲状腺素（TT4）和总三碘甲状腺原氨酸（TT3）。采用实时定量RT-PCR和蛋白质印迹法测量垂体D2以及两种D2特异性泛素连接酶[WD重复序列和含SOCS盒蛋白1（WSB-1）、膜相关环指蛋白（C3HC4）6（MARCH6或TEB4）]和两种D2特异性去泛素化酶[泛素特异性肽酶20（USP20）和泛素特异性肽酶33（USP33）]的mRNA和蛋白质表达水平。还测量了TEB4特异性去泛素化酶USP19的mRNA和蛋白质表达水平。长期高碘摄入显著增加TSH表达。在12周时，6HI、10HI和50HI组的TSH分别是正常碘组的1.57倍、1.44倍和2.11倍。在24周时，50HI组的TSH增加到2.11倍。垂体D2蛋白水平在12周和24周时降低；尽管mRNA水平没有变化。长期碘摄入增加了垂体WSB-1和TEB4的mRNA和蛋白质表达水平。高碘摄入对USP20没有明显影响。观察到USP33和USP19的mRNA水平暂时升高。与D2泛素化相关的酶随长期高碘摄入而变化。D2泛素化增加会抑制D2的活性，导致下丘脑-垂体-甲状腺轴负反馈减少。
