Regulation of CCAAT/Enhancer-binding Protein Homologous Protein (CHOP) Expression by Interleukin-1β in Pancreatic β Cells

Apoptosis contributes to immune-mediated pancreatic beta cell destruction in type I diabetes. Exposure of beta cells to interleukin-1 beta (IL-1 beta) causes endoplasmic reticulum stress and activates proapoptotic networks. Here, we show that nuclear factor kappa B (NF-kappa B) and mitogen-activated protein kinase (MAPK) signaling pathways regulate the expression of CCAAT/enhancer-binding protein homologous protein (CHOP), which mediates endoplasmic reticulum stress-induced apoptosis. Both CHOP mRNA and protein increase in beta cells treated with IL-1 beta. In addition, prolonged exposure to high glucose further increases IL-1 beta-triggered CHOP expression. IL-1 beta also causes increased expression of C/EBP-beta and a reduction of MafA, NFATc2, and Pdx-1 expression in beta cells. Inhibition of the NF-kappa B and MAPK signaling pathways differentially attenuates CHOP expression. Knocking down CHOP by RNA interference protects beta cells from IL-1 beta-induced apoptosis. These studies provide direct mechanistic links between cytokine-induced signaling pathways and CHOP-mediated apoptosis of beta cells.