Department of Pathophysiology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China, 300070.
Free Radic Biol Med. 2012 Apr 15;52(8):1343-52. doi: 10.1016/j.freeradbiomed.2012.02.002. Epub 2012 Feb 11.
Excessive oxidative stress has been suggested as one of the underlying mechanisms in the development of thyroid cytotoxicity. Although the involvement of mitochondria has been hypothesized, the effect of early acute high concentrations of iodide on mitochondrial superoxide production remains largely unknown, especially within a 24 h time frame. By using a novel fluorescent probe, MitoSOX Red, we demonstrated the concentration response and time-course response of KI-induced mitochondrial superoxide production in the Fischer rat thyroid cell line (FRTL). A strong increase of MitoSOX Red fluorescence intensity in FRTL cells can be seen at 2 h following high concentrations of iodide exposure. Besides, we indicated that 6-propyl-2-thiouracil (PTU, 300 μM), thyroid-stimulating hormone (TSH, 10 mU/ml), and perchlorate (KClO(4), 30 μM) can inhibit excessive iodide-induced strong mitochondrial superoxide production; however, diethyldithiocarbamic acid (DETC, 2 mM) can further increase excessive iodide-induced mitochondrial superoxide production. By using transmission electron microscopy (TEM), we noted accumulated myelinoid bodies with lipid droplets and numerous apoptotic nuclear bodies at 24 h in FRTL cells. In addition, we demonstrated a significant decrease in cytochrome c (cyt c) content in the mitochondria by enzyme linked immunosorbent assay (ELISA), and DNA fragments and significant increases in lactate dehydrogenase (LDH) activity were detected. We propose a sequence of events mediated by a strong mitochondrial superoxide production at 2 h, followed by lipid peroxidation, cell membrane damage with significant cyt c release, culminating in DNA fragmentation and apoptotic nuclear formation at 24 h, which may partly contribute to the underlying mechanisms of early acute iodide excess.
过量的氧化应激被认为是甲状腺细胞毒性发展的潜在机制之一。虽然已经假设线粒体参与其中，但在 24 小时的时间范围内，早期急性高浓度碘化物对线粒体超氧化物产生的影响在很大程度上仍然未知。通过使用新型荧光探针 MitoSOX Red，我们证明了 KI 诱导的 Fischer 大鼠甲状腺细胞系 (FRTL) 中线粒体超氧化物产生的浓度反应和时间过程。在高浓度碘化物暴露后 2 小时，FRTL 细胞中的 MitoSOX Red 荧光强度会出现强烈增加。此外，我们表明 6-丙基-2-硫代尿嘧啶 (PTU，300 μM)、促甲状腺激素 (TSH，10 mU/ml) 和高氯酸盐 (KClO4，30 μM) 可以抑制过量碘化物引起的强烈线粒体超氧化物产生；然而，二乙基二硫代氨基甲酸盐 (DETC，2 mM) 可以进一步增加过量碘化物引起的线粒体超氧化物产生。通过使用透射电子显微镜 (TEM)，我们注意到在 FRTL 细胞中 24 小时时积累了具有脂滴的髓样体和大量凋亡核体。此外，我们通过酶联免疫吸附测定 (ELISA) 证明线粒体中细胞色素 c (cyt c) 含量显著下降，并且检测到 DNA 片段和乳酸脱氢酶 (LDH) 活性显著增加。我们提出了一个事件序列，该序列由 2 小时时强烈的线粒体超氧化物产生介导，随后发生脂质过氧化、细胞膜损伤导致大量 cyt c 释放，最终导致 24 小时时 DNA 片段化和凋亡核形成，这可能部分有助于早期急性碘过量的潜在机制。
