title: 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-κB (NF-κB)-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 γ (PPARγ). ER stress-induced IL-8 production was enhanced by NF-κB activation that was negatively regulated by PPARγ. Mechanistically, ER stress-induced CHOP suppressed PPARγ transcription by sequestering C/EBPβ and limiting availability of C/EBPβ binding to the PPARγ promoter. Due to the CHOP-mediated regulation of PPARγ action, ER stress can enhance proinflammatory NF-κB activation and maintain an increased level of IL-8 production in human intestinal epithelial cells. In contrast, PPARγ was a counteracting regulator of gut inflammatory response through attenuation of NF-κB activation. The collective results support the view that balances between CHOP and PPARγ are crucial for epithelial homeostasis, and disruption of these balances in mucosal ER stress can etiologically affect the progress of human inflammatory bowel diseases.
authors.affiliation: Laboratory of Systems Mucosal Biomodulation, Department of Microbiology and Immunology, Pusan National University School of Medicine, Yangsan 626-813, Korea.
authors.forename: Seong-Hwan
authors.initials: SH
authors.lastname: Park
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Choi
authors.forename: Hyun
authors.initials: H
authors.lastname: Yang
authors.forename: Kee Hun
authors.initials: KH
authors.lastname: Do
authors.forename: Juil
authors.initials: J
authors.lastname: Kim
authors.forename: Dong Won
authors.initials: DW
authors.lastname: Lee
authors.forename: Yuseok
authors.initials: Y
authors.lastname: Moon
mesh_terms: D015153:Blotting, Western; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism*
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D016209:Interleukin-8; D016328:NF-kappa B; D047495:PPAR gamma; D051742:Transcription Factor CHOP