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1.  Tumor necrosis factor (TNF)-α-induced IL-8 expression in gastric epithelial cells: Role of reactive oxygen species and AP endonuclease-1/redox factor (Ref)-1 
Cytokine  2009;46(3):359-369.
TNF-α 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-α-induced IL-8 expression in human gastric epithelial cells. We found that TNF-α 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-α treatment whereas Ref-1 suppression and antioxidant treatment inhibited TNF-α-stimulated IL-8 expression. TNF-α-mediated enhancement of other pro-inflammatory chemokines like MIP-3α and Gro-α was also regulated by Ref-1. Although TNF-α increased DNA binding activity of Ref-1-regulated transcription factors, AP-1 and NF-κB, to the IL-8 promoter, promoter activity was mainly mediated by NF-κB binding. Silencing of Ref-1 in AGS cells inhibited basal and TNF-α-induced AP-1 and NF-κB DNA binding activity, but not their nuclear accumulation. Collectively, we provide the first mechanistic evidence of Ref-1 involvement in TNF-α-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.
PMCID: PMC2846768  PMID: 19376732
ROS; Ref-1; TNF-α; IL-8; AGS cell
2.  Modulation of pathogen-induced CCL20 secretion from HT-29 human intestinal epithelial cells by commensal bacteria 
BMC Immunology  2009;10:54.
Human intestinal epithelial cells (IECs) secrete the chemokine CCL20 in response to infection by various enteropathogenic bacteria or exposure to bacterial flagellin. CCL20 recruits immature dendritic cells and lymphocytes to target sites. Here we investigated IEC responses to various pathogenic and commensal bacteria as well as the modulatory effects of commensal bacteria on pathogen-induced CCL20 secretion. HT-29 human IECs were incubated with commensal bacteria (Bifidobacterium infantis or Lactobacillus salivarius), or with Salmonella typhimurium, its flagellin, Clostridium difficile, Mycobacterium paratuberculosis, or Mycobacterium smegmatis for varying times. In some studies, HT-29 cells were pre-treated with a commensal strain for 2 hr prior to infection or flagellin stimulation. CCL20 and interleukin (IL)-8 secretion and nuclear factor (NF)-κB activation were measured using enzyme-linked immunosorbent assays.
Compared to untreated cells, S. typhimurium, C. difficile, M. paratuberculosis, and flagellin activated NF-κB and stimulated significant secretion of CCL20 and IL-8 by HT-29 cells. Conversely, B. infantis, L. salivarius or M. smegmatis did not activate NF-κB or augment CCL20 or IL-8 production. Treatment with B. infantis, but not L. salivarius, dose-dependently inhibited the baseline secretion of CCL20. In cells pre-treated with B. infantis, C. difficile-, S. typhimurium-, and flagellin-induced CCL20 were significantly attenuated. B. infantis did not limit M. Paratuberculosis-induced CCL20 secretion.
This study is the first to demonstrate that a commensal strain can attenuate CCL20 secretion in HT-29 IECs. Collectively, the data indicate that M. paratuberculosis may mediate mucosal damage and that B. infantis can exert immunomodulatory effects on IECs that mediate host responses to flagellin and flagellated enteric pathogens.
PMCID: PMC2763856  PMID: 19814810

Results 1-2 (2)