Acute and long-term effects of arsenite in HepG2 cells

Modulation of insulin signaling

Ingrit Hamann, Kerstin Petroll, Xiaoqing Hou, Anwar Anwar-Mohamed, Ayman O S El-Kadi, Lars Oliver Klotz*

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

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 3′-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.

Original languageEnglish
Pages (from-to)317-332
Number of pages16
JournalBioMetals
Volume27
Issue number2
DOIs
Publication statusPublished - 2014
Externally publishedYes

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Keywords

  • Akt
  • Arsenic
  • FoxO transcription factors
  • HepG2 cells
  • Insulin signaling
  • Selenium homeostasis

Cite this

Hamann, I., Petroll, K., Hou, X., Anwar-Mohamed, A., El-Kadi, A. O. S., & Klotz, L. O. (2014). Acute and long-term effects of arsenite in HepG2 cells: Modulation of insulin signaling. BioMetals, 27(2), 317-332. https://doi.org/10.1007/s10534-014-9714-y