Exploring the effects and mechanism of action of different concentrations of high iodine on NIS in thyroid cells and tissues based on IL-6/STAT3 signaling pathway

Objective: To investigate the effects and mechanism of action of different concentrations of high iodine on Nthy-ori3-1 cells and thyroid tissues of BALB/c mice based on IL-6/STAT3 signaling pathway. Method: Nthy-ori 3-1 cells were cultured in vitro with different concentrations of sodium iodide NaI solution. Thirty BALB/c mice were reared and randomly divided into three groups. Cell proliferation activity was detected by CCK8; apoptosis was detected by flow cytometry; the expression levels of LI-6, STAT3, and NIS were detected by qRT-PCR,WB, immunohistochemical staining and immunofluorescence; the pathomorphological changes of thyroid tissue were observed by HE staining; thyroid function was detected by ELISA. Results: Different concentrations of high iodine inhibited Nthy-ori 3-1 cell proliferation, induced apoptosis and secretion of inflammatory factors to different degrees (P<0.001); Nthy-ori 3-1 cells cultured with high iodine (1 mM NaI) were stimulated with different concentrations of IL-6 and STAT3 reagents, and the expression of NIS decreased; whereas the expression of NIS was increased by the administration of STAT3 inhibitor (P<0.05). The levels of IL-6 and STAT3 in the 10HI and 100HI groups were significantly higher than those in the NC group (P<0.05). HE showed that high iodine damaged follicles of thyroid tissues, and WB, PCR, and immunohistochemistry showed that with the increase of iodine concentration, the expression of IL-6 and STAT3 and the expression of NIS were increased in thyroid tissues. STAT3 expression increased and NIS expression decreased with increasing iodine concentration (P<0.05); immunofluorescence and WB showed that NIS expression in thyroid tissue was enhanced after injection of STAT3 inhibitor (P<0.05). Conclusions: 1. Excessive iodine concentrations promoted the expression of IL-6 and STAT3 and inhibited the expression of NIS. 2. Excessive iodine may inhibit thyroid NIS expression by activating the IL-6/STAT3 pathway.