碘过量对胰岛β细胞功能的影响及机制

Effects of iodine excess on islet β cells(β-TC-6) function and the mechanism

目的探索碘过量暴露对小鼠胰岛素瘤细胞系β-TC-6胰岛素分泌功能影响及机制。方法β-TC-6细胞在对数生长期暴露于0、0.01、0.1、1、10和100 mmol/L碘24 h,采用四氮唑盐(MTT)比色法检测细胞存活率。细胞经0.01、1、和100 mmol/L碘干预24 h后,用5.6 mmol/L葡萄糖刺激细胞1 h,酶联免疫分析(ELISA)法检测上清胰岛素含量。蛋白印迹法(Western blot)检测GRP78、IRE1α、Bcl-2和Bax蛋白表达。结果与对照组比较,1~100 mmol/L碘处理组细胞存活率显著降低(P<0.05);1 mmol/L组细胞胰岛素分泌量显著增加(P<0.05),100 mmol/L组细胞胰岛素分泌量显著下降(P<0.05),1和10 mmol/L组GRP78、IRE1α和Bax蛋白表达量显著增加(P<0.05),而Bcl-2蛋白表达显著降低(P<0.05)。5.6 mmol/L葡萄糖+0 mmol/L碘组、5.6 mmol/L葡萄糖+0.01 mmol/L碘组和5.6 mmol/L葡萄糖+1 mmol/L碘组分别与相应对照组比较,细胞胰岛素分泌量组间差异显著(P<0.05)。结论过量碘可降低β-TC-6细胞胰岛素分泌量,损害胰岛素分泌功能,其机制很可能与内质网应激和Bcl-2/Bax蛋白表达比例失衡密切相关。

Objective To explore the influences of iodine excess on insulin secret function of mouse insulinoma cells β-TC-6 and the mechanism. Methods β-TC-6 cells were treated with excessive iodine（ Na I） in vitro. After 24 hour of exposure,the MTT assay was used to measure the cell viabilities. β-TC-6 cells,after 24 hour of exposure in excessive iodine, were stimulated with Krebs-Ringer bicarbonate buffer containing 5. 6mmol/L glucose for 1 hour at 37 ℃,then the supernatant was collected for insulin determination by ELISA kit. Western blot was used to detect the expression of Bcl-2,Bax,GRP78 and IRE1α. Results The rate of cell viability decreased from 1 mmol/L to 100mmol/L iodine excess group by a dose-dependent manner and was significantly lower than the control group and as follow by 73. 3%,71. 2% and 55. 8% of that of control group. Iodine excess impaired the insulin secret function of β-TC-6 cells in 1 mmol/L and 100 mmol/L iodine excess groups. The expression of Bcl-2 decreased while the expressionof Bax increased significantly when compared with control group（ P 0. 05）. From 1mmol/L iodine excess group, the expression of GRP78 and IRE1α were increased significantly when compared with control group（ P 0. 05）. Conclusion Iodine excess decreased the cell viabilities and impaired insulin secret function,which might be related to endoplasmic reticulum stress and Bcl-2 families.