Endoplasmic reticulum stress-activated C/EBP homologous protein enhances nuclear factor-kappaB signals via repression of peroxisome proliferator-activated receptor gamma.

ABSTRACT: Endoplasmic reticulum (ER) stress is a causative factor of inflammatory bowel diseases. ER stress mediators, including CCAAT enhancer-binding protein (C/EBP) homologous protein (CHOP), are elevated in intestinal epithelia from patients with inflammatory bowel diseases. The present study arose from the question of how chemical ER stress and CHOP protein were associated with nuclear factor-?B (NF-?B)-mediated epithelial inflammatory response. In a human intestinal epithelial cell culture model, chemical ER stresses induced proinflammatory cytokine interleukin-8 (IL-8) expression and the nuclear translocation of CHOP protein. CHOP was positively involved in ER-activated IL-8 production and was negatively associated with expression of peroxisome proliferator-activated receptor ? (PPAR?). ER stress-induced IL-8 production was enhanced by NF-?B activation that was negatively regulated by PPAR?. Mechanistically, ER stress-induced CHOP suppressed PPAR? transcription by sequestering C/EBP? and limiting availability of C/EBP? binding to the PPAR? promoter. Due to the CHOP-mediated regulation of PPAR? action, ER stress can enhance proinflammatory NF-?B activation and maintain an increased level of IL-8 production in human intestinal epithelial cells. In contrast, PPAR? was a counteracting regulator of gut inflammatory response through attenuation of NF-?B activation. The collective results support the view that balances between CHOP and PPAR? are crucial for epithelial homeostasis, and disruption of these balances in mucosal ER stress can etiologically affect the progress of human inflammatory bowel diseases.

SUBMITTER: Park SH 

PROVIDER: S-EPMC2975157 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature