Deficiency of long isoforms of Nfe2l1 sensitizes MIN6 pancreatic β cells to arsenite-induced cytotoxicity

Toxicol Appl Pharmacol. 2017 Aug 15;329:67-74. doi: 10.1016/j.taap.2017.05.013. Epub 2017 May 24.

Abstract

Increasing evidence indicates that chronic inorganic arsenic exposure is associated with type 2 diabetes (T2D), a disease of growing prevalence. Pancreatic β-cells were targeted and damaged by oxidative stress induced by arsenite. We previously showed that nuclear factor erythroid 2 like 2 (Nfe2l2)-deficient pancreatic β-cells were vulnerable to cell damage induced by oxidative stressors including arsenite, due to a muted antioxidant response. Like nuclear factor erythroid 2 like 2 (NFE2L2), NFE2L1 also belongs to the cap 'n' collar (CNC) basic-region leucine zipper (bZIP) transcription factor family, and regulates antioxidant response element (ARE) related genes. Our prior work showed NFE2L1 regulates glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells and isolated islets. In the current study, we demonstrated that MIN6 cells with a specific knockdown of long isoforms of Nfe2l1 (L-Nfe2l1) by lentiviral shRNA (Nfe2l1(L)-KD) were vulnerable to arsenite-induced apoptosis and cell damage. The expression levels of antioxidant genes, such as Gclc, Gclm and Ho-1, and intracellular reactive oxygen species (ROS) levels were not different in Scramble and Nfe2l1(L)-KD cells, while the expression of arsenic metabolism related-genes, such as Gsto1, Gstm1 and Nqo1, increased in Nfe2l1(L)-KD cells with or without arsenite treatment. The up-regulation of arsenic biotransformation genes was due to activated NFE2L2 in Nfe2l1(L)-KD MIN6 cells. Furthermore, the level of intracellular monomethylarsenic (MMA) was higher in Nfe2l1(L)-KD MIN6 cells than in Scramble cells. These results showed that deficiency of L-Nfe2l1 in pancreatic β-cells increased susceptibility to acute arsenite-induced cytotoxicity by promoting arsenic biotransformation and intracellular MMA levels.

Keywords: Arsenite; Cytotoxicity; MIN6; Nfe2l1; Pancreatic β-cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arsenites / metabolism
  • Arsenites / toxicity*
  • Biotransformation / genetics
  • Cell Line
  • Cell Survival / drug effects
  • Gene Expression Regulation, Enzymologic
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / enzymology
  • Insulin-Secreting Cells / pathology
  • Methylation
  • Mice
  • NF-E2-Related Factor 1 / deficiency*
  • NF-E2-Related Factor 1 / genetics
  • Oxidative Stress / drug effects
  • Protein Isoforms
  • RNA Interference
  • RNA, Messenger / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects
  • Sodium Compounds / metabolism
  • Sodium Compounds / toxicity*
  • Transfection

Substances

  • Arsenites
  • NF-E2-Related Factor 1
  • Nfe2L1 protein, mouse
  • Protein Isoforms
  • RNA, Messenger
  • Reactive Oxygen Species
  • Sodium Compounds
  • sodium arsenite