title: TNF-alpha-induced up-regulation of pro-inflammatory cytokines is reduced by phosphatidylcholine in intestinal epithelial cells.
abstract: BACKGROUND
  Phosphatidylcholine (PC) is a major lipid of the gastrointestinal mucus layer. We recently showed that mucus from patients suffering from ulcerative colitis has low levels of PC. Clinical studies reveal that the therapeutic addition of PC to the colonic mucus using slow release preparations is beneficial. The positive role of PC in this disease is still unclear; however, we have recently shown that PC has an intrinsic anti-inflammatory property. It could be demonstrated that the exogenous application of PC inhibits membrane-dependent actin assembly and TNF-alpha-induced nuclear NF-kappaB activation. We investigate here in more detail the hypothesis that the exogenous application of PC has anti-inflammatory properties.
  
  
  METHODS
  PC species with different fatty acid side chains were applied to differentiated and non-differentiated Caco-2 cells treated with TNF-alpha to induce a pro-inflammatory response. We analysed TNF-alpha-induced NF-kappaB-activation via the transient expression of a NF-kappaB-luciferase reporter system. Pro-inflammatory gene transcription was detected with the help of a quantitative real time (RT)-PCR analysis. We assessed the binding of TNF-alpha to its receptor by FACS and analysed lipid rafts by isolating detergent resistant membranes (DRMs).
  
  
  RESULTS
  The exogenous addition of all PC species tested significantly inhibited TNF-alpha-induced pro-inflammatory signalling. The expression levels of IL-8, ICAM-1, IP-10, MCP-1, TNF-alpha and MMP-1 were significantly reduced after PC pre-treatment for at least two hours. The effect was comparable to the inhibition of NF-kB by the NF-kB inhibitor SN 50 and was not due to a reduced binding of TNF-alpha to its receptor or a decreased surface expression of TNF-alpha receptors. PC was also effective when applied to the apical side of polarised Caco-2 cultures if cells were stimulated from the basolateral side. PC treatment changed the compartmentation of the TNF-alpha-receptors 1 and 2 to DRMs.
  
  
  CONCLUSIONS
  PC induces a prolonged inhibition of TNF-alpha-induced pro-inflammatory signalling. This inhibition may be caused by a shift of the TNF-alpha receptors at the surface to lipid rafts. Our results may offer a potential molecular explanation for the positive role of PC seen in clinical studies for the treatment of ulcerative colitis.
authors: Department of Gastroenterology, University of Heidelberg, Heidelberg, Germany. irina_treede@med.uni-heidelberg.de
authors: Irina
authors: I
authors: Treede
authors: Annika
authors: A
authors: Braun
authors: Petia
authors: P
authors: Jeliaskova
authors: Thomas
authors: T
authors: Giese
authors: Joachim
authors: J
authors: Füllekrug
authors: Gareth
authors: G
authors: Griffiths
authors: Wolfgang
authors: W
authors: Stremmel
authors: Robert
authors: R
authors: Ehehalt
mesh_terms: D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010713:Phosphatidylcholines / Q000494:pharmacology*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: C111835:CCL2 protein, human; D018932:Chemokine CCL2; D016207:Cytokines; D016209:Interleukin-8; D016328:NF-kappa B; D010713:Phosphatidylcholines; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D020781:Matrix Metalloproteinase 1