Tumor necrosis factor (TNF)-alpha-induced IL-8 expression in gastric epithelial cells: role of reactive oxygen species and AP endonuclease-1/redox factor (Ref)-1.
TNF-alpha contributes to oxidative stress via induction of reactive oxygen species (ROS) and pro-inflammatory cytokines. The molecular basis of this is not well understood but it is partly mediated through the inducible expression of IL-8. As redox factor-1 (Ref-1), is an important mediator of redox-regulated gene expression we investigated whether ROS and Ref-1 modulate TNF-alpha-induced IL-8 expression in human gastric epithelial cells. We found that TNF-alpha treatment of AGS cells enhanced nuclear expression of Ref-1 and potently induced IL-8 expression. Overexpression of Ref-1 enhanced IL-8 gene transcription at baseline and after TNF-alpha treatment whereas Ref-1 suppression and antioxidant treatment inhibited TNF-alpha-stimulated IL-8 expression. TNF-alpha-mediated enhancement of other pro-inflammatory chemokines like MIP-3 alpha and Gro-alpha was also regulated by Ref-1. Although TNF-alpha increased DNA binding activity of Ref-1-regulated transcription factors, AP-1 and NF-kappaB, to the IL-8 promoter, promoter activity was mainly mediated by NF-kappaB binding. Silencing of Ref-1 in AGS cells inhibited basal and TNF-alpha-induced AP-1 and NF-kappaB DNA binding activity, but not their nuclear accumulation. Collectively, we provide the first mechanistic evidence of Ref-1 involvement in TNF-alpha-mediated, redox-sensitive induction of IL-8 and other chemokines in human gastric mucosa. This has implications for understanding the pathogenesis of gastrointestinal inflammatory disorders.
O'Hara
Ann M
AM
Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
Bhattacharyya
Asima
A
Bai
Jie
J
Mifflin
Randy C
RC
Ernst
Peter B
PB
Mitra
Sankar
S
Crowe
Sheila E
SE
D000111:Acetylcysteine / Q000378:metabolism; D002478:Cells, Cultured; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000378:metabolism; D005753:Gastric Mucosa / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
D016166:Free Radical Scavengers; D016209:Interleukin-8; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D000111:Acetylcysteine