The Mechanism Of Nthy-ori3-1Cell Apoptosis Induced By Excessive Iodine

Excessive iodine intake can not only cause thyroid disfunction and hyperthyroidism, but also damege thyroid. The mechanism of the damage is still not clear yet; there are a lot of controversies. In recent years, scholars have focused on thyroid cell apoptosis caused by different doses of iodine intake. Vitale M confirmed that excessive iodine can influence the generation of reactive oxygen species(ROS), inhibit thyroid cell growth and even cause apoptosis or necrosis; it also can interfere thyroid cell cycle, causing the cell stagnation in G0/G1and G2/M phase. Lin and Xu found that excessive iodine can adjust the expression of Fas, FasL, Bcl2and Bax, so as to promote apoptosis.Endoplasmic reticulum located near the Nucleus. It is the most important Ca2+storage device of mammalian cell, and an important place for protein synthesis and modification. Oxidative stress, chemical poisons can change the microenvironment of Endoplasmic reticulum, causing misfolded and unfolded protein with Ca2+balance disorders, leading to endoplasmic reticulum stress (ERS). Researches show that there are three classic pathways of apoptosis:mitochondrial pathway, death receptor pathway and endoplasmic reticulum pathway. There are kinds of connections among these three classic pathways. Researchers believe that the excessive iodine induced thyroid apoptosis occurs mainly via the mitochondrial and death receptor pathway, but whether the endoplasmic reticulum pathway influence human thyroid cell apoptosis, there have been little studies.ObjectiveThe purpose of this study was to determine the effects of different doses of iodine on thyroid cells in vitro models and to investigate the iodine-induced apoptosis in thyroid cells through the endoplasmic reticulum pathway and provide a theoretical basis for the prevention of the toxic effects of high iodine on the thyroid.Methods1Nthy-ori3-1cells were exposed to0,1,10,50mmol/L of potassium iodide in vitro. After24hours incubation, lactate dehydrogenase (LDH) assay were used to measure the LDH leakage rate.2Reactive oxygen species (ROS) level, constituent ratio of the cell cycle, and apoptosis rate were measured by flow cytometry.3Nthy-ori3-1cells were exposed to0,1,10,50mmol/L of potassium iodide in vitro. After24hours incubation, total RNA was extracted and RT-PCR was used for GRP78, IRE1, XBP-1(S) and CHOP mRNA detection.4Nthy-ori3-1cells were exposed to0,1,10,50mmol/L of potassium iodide in vitro. After24hours incubation,Total protein was extracted and GRP78, IRE1and CHOP protein were detected by Western blot.Results1After treating for24h, compared to control group,1,10mmol/L potassium iodide-treated group, the LDH leakage rate and the precentage of apoptosis cells of the50mmol/L fluoride-treated groups were significantly increased (P<0.05).2After treating for24h with different doses of fluoride, ROS level of the different potassium iodide-treated group have no significantly change (P>0.05).3After treating for24h, The Go/Gi phase cells of the50mmol/L potassium iodide-treated group were higher (P<0.05) than the other groups but the percentage of cells in S phase were lower(P<0.05) than the other groups.4After treating for24h, the expression of GRP78, IRE1and XBP-1(S) mRNA of the different potassium iodide-treated group have no significantly change (P>0.05) than the control group; The expression of CHOP mRNA were higher than the control group (P<0.05).5After treating for24h, the expression of GRP78, IRE1and CHOP protein of the different potassium iodide-treated group have no significantly change (P>0.05) than the control group.Conclusions1Excessive iodine can decrease cell viability and increase LDH leakage rate, causing thyroid cell damage,blocks the cells in Go/Gi phase, and induce Nthy-ori3-1cell apoptosis. 2Excessive iodine may not increase Nthy-ori3-1cell ROS level. This may be related to cell species. Further researches is required.3Excessive iodine doesn’t activate the endoplasmic reticulum stress reaction, and the latter may not participate in the process of high iodine induce Nthy-ori3-1cell apoptosis.This work was supported by grants from National Natural Science Foundation of China(No.30972555).