Kolypetri Panayota, Carayanniotis George
Divisions of Endocrinology and Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland , St. John's, Canada .
Thyroid. 2014 Jul;24(7):1170-8. doi: 10.1089/thy.2013.0676. Epub 2014 May 28.
Enhanced iodide intake in NOD.H2(h4) mice accelerates the incidence and severity of spontaneous autoimmune thyroiditis (SAT) via an unknown mechanism. A plausible hypothesis is that iodide-induced apoptosis of thyrocytes can create imbalances in antigenic load and/or disruption of immunoregulatory mechanisms that facilitate activation of autoreactive T cells in cervical lymph nodes draining the thyroid.
We examined whether NOD.H2(h4) thyrocytes, exposed to low NaI concentrations in vitro, are more susceptible to apoptosis compared to thyrocytes from CBA/J mice, which are resistant to iodide-accelerated SAT (ISAT). We also looked, at the transcriptional level, for differential activation of genes involved in apoptosis or oxidative stress pathways that may account for potential differences in iodide-mediated apoptosis between NOD.H2(h4) and CBA/J thyrocytes.
We report that NOD.H2(h4) thyrocytes, cultured for 24 h at very low (4-8 μM) concentrations of NaI, exhibit high levels (40-55%) of apoptosis, as assessed microscopically following staining with fluorescent caspase inhibitors. Similar treatment of thyrocytes from CBA/J mice, which are resistant to ISAT, yielded significantly lower (10-20%) apoptotic rates. Expression analysis by real-time polymerase chain reaction using arrays of apoptosis- and oxidative stress-related genes showed that NaI intake upregulates the expression of 22 genes involved in ROS metabolism and/or antioxidant function in CBA/J thyrocytes, whereas only two of these genes were upregulated in NOD.H2(h4) thyrocytes. Among the set of overexpressed genes were those encoding thyroid peroxidase (Tpo; 5.77-fold), glutathione peroxidases (Gpx2, Gpx4, Gpx7; 2.03-3.14-fold), peroxiredoxins (Prdx1, Prdx2, Prdx5; 2.27-2.97-fold), superoxide dismutase 1 (Sod1; 3.57-fold), thioredoxin 1 (Txn1; 2.13-fold), and the uncoupling proteins 2 and 3 (Ucp2, Ucp3; 2.01-2.15-fold).
The results demonstrate that an impaired control of oxidative stress mechanisms is associated with the observed high susceptibility of NOD.H2(h4) thyrocytes to NaI-mediated apoptosis, and suggest a contributing factor for the development of ISAT in this strain.
在NOD.H2（h4）小鼠中，碘摄入量增加会通过未知机制加速自发性自身免疫性甲状腺炎（SAT）的发病和严重程度。一个合理的假设是，碘诱导的甲状腺细胞凋亡会导致抗原负荷失衡和/或免疫调节机制破坏，从而促进甲状腺引流颈部淋巴结中自身反应性T细胞的激活。
我们研究了体外暴露于低浓度碘化钠（NaI）的NOD.H2（h4）甲状腺细胞与对碘加速性SAT（ISAT）有抗性的CBA/J小鼠的甲状腺细胞相比，是否更易发生凋亡。我们还在转录水平上研究了参与凋亡或氧化应激途径的基因的差异激活情况，这些基因可能解释NOD.H2（h4）和CBA/J甲状腺细胞在碘介导的凋亡方面的潜在差异。
我们报告，在极低（4 - 8 μM）浓度的NaI中培养24小时的NOD.H2（h4）甲状腺细胞，经荧光半胱天冬酶抑制剂染色后显微镜评估显示，凋亡水平很高（40 - 55%）。对抵抗ISAT的CBA/J小鼠的甲状腺细胞进行类似处理，凋亡率显著较低（10 - 20%）。使用凋亡和氧化应激相关基因阵列通过实时聚合酶链反应进行的表达分析表明，NaI摄入上调了CBA/J甲状腺细胞中22个参与活性氧（ROS）代谢和/或抗氧化功能的基因的表达，而在NOD.H2（h4）甲状腺细胞中仅上调了其中两个基因。在过表达的基因中，有编码甲状腺过氧化物酶（Tpo；5.77倍）、谷胱甘肽过氧化物酶（Gpx2、Gpx4、Gpx7；2.03 - 3.14倍）、过氧化物还原酶（Prdx1、Prdx2、Prdx5；2.27 - 2.97倍）、超氧化物歧化酶1（Sod1；3.57倍）、硫氧还蛋白1（Txn1；2.13倍）以及解偶联蛋白2和3（Ucp2、Ucp3；2.01 - 2.15倍）的基因。
结果表明，氧化应激机制控制受损与观察到的NOD.H2（h4）甲状腺细胞对NaI介导的凋亡高度敏感性相关，并提示了该品系中ISAT发生的一个促成因素。
