Acute and long-term effects of arsenite in HepG2 cells: modulation of insulin signaling
Acute and long-term effects of arsenite in HepG2 cells: modulation of insulin signaling
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DOI：
10.1007/s10534-014-9714-y
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发表时间：
2014-04-01
期刊：
影响因子：
3.5
通讯作者：
Klotz, Lars-Oliver
中科院分区：
文献类型：
--
作者：
Hamann, Ingrit;Petroll, Kerstin;Klotz, Lars-Oliver
流行病学研究表明，糖尿病患病率与砷暴露之间存在关系。砷可能导致这种糖尿病效应的机制在很大程度上还不清楚。磷脂酰肌醇30-激酶(PI3K)/Akt信号通路通过调节FoxO转录因子的活性，调控糖代谢，在胰岛素信号转导中发挥重要作用。本研究旨在探讨短期和长期亚砷酸盐暴露对人肝癌细胞株HepG2细胞胰岛素信号转导的影响、PI3K/Akt信号转导途径的作用以及胰岛素调控的靶基因的调控。细胞暴露于亚砷酸盐24小时后，细胞对胰岛素刺激Akt的反应减弱。同时，短期暴露于亚砷酸盐诱导Akt在Ser-473的磷酸化程度呈浓度依赖性增加，随后在已知被Akt磷酸化的位置发生FoxO蛋白的磷酸化。Wortmannin阻止了Foxos的磷酸化，表明PI3K参与了Foxos的磷酸化。亚砷酸盐暴露导致FoxO DNA结合减弱和FoxO1a-EGFP的核排斥。亚微摩尔浓度的亚砷酸盐作用于HepG2细胞24小时，导致葡萄糖6-磷酸酶(G6Pase)和硒蛋白P(SELP)基因表达下调。奇怪的是，亚砷酸盐对SELP蛋白水平有双重影响，导致纳摩尔浓度范围的小幅增加和微摩尔浓度范围的显著降低。有趣的是，亚砷酸盐诱导的对G6Pase和SELP mRNA或SELP蛋白水平的长期影响不能被PI3K抑制剂wortmannin阻断。总而言之，亚砷酸盐扰乱了参与燃料代谢的细胞信号通路：它削弱了细胞对胰岛素的反应，同时刺激胰岛素样信号来减弱参与葡萄糖代谢的基因的表达和肝细胞因子SELP的释放，后者被认为是调节外周胰岛素敏感性的。
Epidemiological studies have indicated a relationship between the prevalence of diabetes and exposure to arsenic. Mechanisms by which arsenic may cause this diabetogenic effect are largely unknown. The phosphoinositide 30-kinase (PI3K)/Akt signaling pathway plays an important role in insulin signaling by controlling glucose metabolism, in part through regulating the activity of FoxO transcription factors. The present study aimed at investigating the effect of short and long-term exposure to arsenite on insulin signaling in HepG2 human hepatoma cells, the role of PI3K/Akt signaling therein and the modulation of target genes controlled by insulin. Exposure of cells to arsenite for 24 h rendered cells less responsive toward stimulation of Akt by insulin. At the same time, short-term exposure to arsenite induced a concentration-dependent increase in phosphorylation of Akt at Ser-473, followed by phosphorylation of FoxO proteins at sites known to be phosphorylated by Akt. Phosphorylation of FoxOs was prevented by wortmannin, pointing to the involvement of PI3K. Arsenite exposure resulted in attenuation of FoxO DNA binding and in nuclear exclusion of FoxO1a-EGFP. A 24-h exposure of HepG2 cells to submicromolar concentrations of arsenite resulted in downregulation of glucose 6-phosphatase (G6Pase) and selenoprotein P (SelP) mRNA levels. Curiously, arsenite had a dual effect on SelP protein levels, inducing a small increase in the nanomolar and a distinct decrease in the micromolar concentration range. Interestingly, arsenite-induced long-term effects on G6Pase and SelP mRNA or SelP protein levels were not blocked by the PI3K inhibitor, wortmannin. In conclusion, arsenite perturbs cellular signaling pathways involved in fuel metabolism: it impairs cellular responsiveness toward insulin, while at the same time stimulating insulin-like signaling to attenuate the expression of genes involved in glucose metabolism and the release of the hepatokine SelP, which is known to modulate peripheral insulin sensitivity.