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

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.