Cystic fibrosis (CF) is characterized by a dramatic neutrophil recruitment and repeated Pseudomonas infections in the lungs. To evaluate cytokine releasibility by airway epithelial cells in the context of CF, we studied primary nasal epithelial cells isolated from the upper airways and continuous epithelial cell lines from normal and CF subjects. Relatively low levels of interleukin (IL)-8, IL-6, and granulocyte/macrophage colony-stimulating factor (GM-CSF) were produced spontaneously by primary epithelial cells (< 50 pg/10(6) cells) and higher levels of colony-stimulating factor-1 (CSF-1) (1 to 2 ng/10(6) cells). Cells were stimulated with substances that are likely to be present in the inflamed lungs of CF patients-namely, the proinflammatory monokines IL-1 and tumor necrosis factor-alpha (TNF alpha) as well as neutrophil elastase and bacterial products from Pseudomonas (mucoid exopolysaccharide [MEP] and rhamnolipids). Both IL-1 and TNF alpha induced a dose-dependent release of IL-6 (5 to 10 ng/10(6) cells) and GM-CSF (2 to 3 ng/10(6) cells) by primary epithelial cells from eight normal volunteers. The TNF alpha/IL-1-stimulated GM-CSF release was blocked by the addition of 1 microM dexamethasone, whereas basal CSF-1 release was unaffected. Neutrophil elastase was a potent inducer of IL-8 and GM-CSF both in primary epithelial cells and in cell lines. Dexamethasone (1 microM) did not inhibit elastase-induced IL-8 release in either normal or CF epithelial cells. Rhamnolipids and MEP were found to stimulate the copious release of IL-8, GM-CSF, and IL-6 from epithelial cells, in a steroid-sensitive fashion.(ABSTRACT TRUNCATED AT 250 WORDS)
The intestinal epithelium is continuously and rapidly renewed by a process involving cell generation, migration, and differentiation, from the stem cell population located at the bottom of the crypt to the extrusion of the terminally differentiated cells at the tip of the villus. Because of the lack of normal human intestinal cell models, most of our knowledge about the regulation of human intestinal cell functions has been derived from studies conducted on cell cultures generated from experimental animals and human colon cancers. However, important advances have been achieved over recent years in the generation of normal human intestinal cell models. These models include (a) intestinal cell lines with typical crypt cell proliferative noncommitted characteristics, (b) conditionally immortalized intestinal cell lines that can be induced to differentiate, and (c) primary cultures of differentiated villuslike cells that can be maintained in culture for up to 10 days. Each of these models should help in the investigation of the specific aspects of human intestinal function and regulation. Furthermore, taken together, these models provide an integrated system that allows an in vitro recapitulation of the entire crypt-villus axis of the normal human small intestine.
In the intestinal epithelium, the Cdx, GATA, and HNF transcription factor families are responsible for the expression of differentiation markers such as sucrase-isomaltase. Although previous studies have shown that Cdx2 can induce differentiation in rat intestinal IEC-6 cells, no data are available concerning the direct implication of transcription factors on differentiation in human normal intestinal epithelial cell types. We investigated the role of Cdx2, GATA-4, and HNF-1α using the undifferentiated human intestinal epithelial crypt cell line HIEC. These transcription factors were tested on proliferation and expression of polarization and differentiation markers. Ectopic expression of Cdx2 or HNF-1α, alone or in combination, altered cell proliferation abilities through the regulation of cyclin D1 and p27 expression. HNF-1α and GATA-4 together induced morphological modifications of the cells toward polarization, resulting in the appearance of functional features such as microvilli. HNF-1α was also sufficient to induce the expression of cadherins and dipeptidylpeptidase, whereas in combination with Cdx2 it allowed the expression of the late differentiation marker sucrase-isomaltase. Large-scale analysis of gene expression confirmed the cooperative effect of these factors. Finally, although DcamKL1 and Musashi-1 expression were downregulated in differentiated HIEC, other intestinal stem cell markers, such as Bmi1, were unaffected. These observations show that, in cooperation with Cdx2, HNF-1α acts as a key factor on human intestinal cells to trigger the onset of their functional differentiation program whereas GATA-4 appears to promote morphological changes.
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