Human colon fibroblasts induce differentiation and proliferation of intestinal epithelial cells through the direct paracrine action of keratinocyte growth factor

Epidermal growth factor (EGF) is one of the trophic factors for intestinal adaptation after small bowel transplantation (SBT). A recent report indicates that nitric oxide (NO) has cytoprotective effects on bacterial translocation (BT) after SBT. We hypothesized that EGF stimulates the expression of the inducible NO synthase (iNOS) gene in the graft after SBT, followed by increased production of NO, resulting in the decrease of BT. Intestinal epithelial cells (IEC)-6 were treated with EGF and/or IL-1β in the presence and absence of phosphatidylinositol 3-kinase (PI3-kinase) and EGF receptor kinase inhibitors (LY-294002 and tyrphostin A25). The induction of NO production and iNOS and its signal molecules, including the inhibitory protein of NF-κB (IκB), NF-κB, and Akt, were analyzed. IL-1β stimulated the degradation of IκB and the activation of NF-κB but had no effect on iNOS induction. EGF, which had no effect on the NF-κB activation and iNOS induction, stimulated the upregulation of type 1 IL-1 receptor (IL-1R1) through PI3-kinase/Akt. Simultaneous addition of EGF and IL-1β stimulated synergistically the induction of iNOS, leading to the increased production of NO. Our results indicate that EGF and IL-1β stimulate two essential signals for iNOS induction in IEC-6 cells: the upregulation of IL-1R1 through PI3-kinase/Akt and the activation of NF-κB through IκB kinase, respectively. Simultaneous addition of EGF and IL-1β can enhance the production of NO, which may contribute to the cytoprotective effect of EGF against intestinal injury.

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Proinflammatory cytokines TNF-α and IFN-γ alter laminin expression under an apoptosis-independent mechanism in human intestinal epithelial cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00535.2003 ◽

2004 ◽

Vol 287 (3) ◽

pp. G592-G598 ◽

Cited By ~ 34

Author(s):

Caroline Francoeur ◽

Fabrice Escaffit ◽

Pierre H. Vachon ◽

Jean-François Beaulieu

Keyword(s):

Growth Factor ◽

Epithelial Cells ◽

Proinflammatory Cytokines ◽

Intestinal Epithelial Cells ◽

Intestinal Epithelial ◽

Laminin 5 ◽

Cell Functions ◽

Tnf Α ◽

Independent Mechanism ◽

Ifn Γ

Laminins are basement membrane molecules that mediate cell functions such as adhesion, proliferation, migration, and differentiation. In the normal small intestine, laminin-5 and -10 are mainly expressed at the base of villus cells. However, in Crohn's disease (CD), a major redistribution of these laminins to the crypt region of the inflamed ileal mucosa has been observed, suggesting a possible relationship between laminin expression and cytokine and/or growth factor production, which is also altered in CD. The aim of this study was to test the hypothesis that proinflammatory cytokines can modulate laminin expression by intestinal epithelial cells. The effect of TNF-α, IFN-γ, IL-1β, IL-6, and transforming growth factor (TGF)-β was analyzed on the expression of laminins in the normal human intestinal epithelial crypt (HIEC) cell line. When treated with a single cytokine, HIEC cells secreted small amounts of laminin-5 and -10. Only TNF-α and TGF-β induced a slight increase in the secretion of these laminins. However, in combination, TNF-α and IFN-γ synergistically stimulated the secretion of both laminin-5 and -10 in HIEC cells. Transcript analyses suggested that the upregulation of the two laminins might depend on distinct mechanisms. Interestingly, the TNF-α and IFN-γ combination was also found to significantly promote apoptosis. However, the effect of cytokines on the secretion of laminins was maintained even after completely blocking apoptosis by inhibiting caspase activities. These results demonstrate that laminin production is specifically modulated by the proinflammatory cytokines TNF-α and IFN-γ in intestinal epithelial cells under an apoptosis-independent mechanism.

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