Abstract
We previously reported that the enterocytic differentiation of human colonic Caco-2 cells correlated with alterations in integrin signaling. We now investigated whether differentiation and apoptosis of Caco-2 cells induced by the short-chain fatty acid butyrate (NaBT) was associated with alterations in the integrin-mediated signaling pathway with special interest in the expression and activity of focal adhesion kinase (FAK), of the downstream phosphatidylinositol 3'-kinase (PI 3-kinase)-Akt pathway and in the role of the nuclear factor kappaB (NF-kappaB). NaBT increased the level of sucrase. It induced apoptosis as shown by: (1) decreased Bcl-2 and Bcl-X(L) proteins and increased Bax protein; (2) activation of caspase-3; and (3) increased shedding of apoptotic cells in the medium. This effect was associated with defective integrin-mediated signaling as shown by: (1) down-regulation of beta1 integrin expression; 2) decreased FAK expression and tyrosine phosphorylation; (3) concerted alterations in cytoskeletal and structural focal adhesions proteins (talin, ezrin); and (4) decreased FAK ability to associate with PI 3-kinase. However, in Caco-2 cells, beta1-mediated signaling failed to be activated downstream of FAK and PI 3-kinase at the level of Akt. Transfection studies show that NaBT treatment of Caco-2 cells promoted a significant activation of the NF-kappaB which was probably involved in the NaBT-induced apoptosis. Our results indicate that the prodifferentiating agent NaBT induced apoptosis of Caco-2 cells probably through NF-kappaB activation together with a defective beta1 integrin-FAK-PI 3-kinase pathways signaling.
MeSH terms
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Apoptosis / drug effects
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Apoptosis / physiology*
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Butyrates / pharmacology
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Caco-2 Cells
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Carcinoma / drug therapy
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Carcinoma / metabolism
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Carcinoma / physiopathology
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Caspase 3
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Caspases / drug effects
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Caspases / metabolism
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Cell Adhesion / drug effects
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Cell Adhesion / physiology*
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Cell Differentiation / drug effects
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Cell Differentiation / physiology*
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Colonic Neoplasms / drug therapy
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Colonic Neoplasms / metabolism
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Colonic Neoplasms / physiopathology
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Down-Regulation / drug effects
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Down-Regulation / physiology
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Focal Adhesion Kinase 1
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Focal Adhesion Protein-Tyrosine Kinases
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Humans
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Integrin beta1 / drug effects
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Integrin beta1 / metabolism
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Integrins / drug effects
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Integrins / metabolism*
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Intestinal Mucosa / drug effects
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Intestinal Mucosa / metabolism*
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NF-kappa B / drug effects
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NF-kappa B / metabolism
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Phosphatidylinositol 3-Kinases / drug effects
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphorylation / drug effects
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Protein Serine-Threonine Kinases*
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Protein-Tyrosine Kinases / drug effects
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Protein-Tyrosine Kinases / metabolism
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Proto-Oncogene Proteins / drug effects
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins c-bcl-2 / drug effects
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Sucrase / drug effects
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Sucrase / metabolism
Substances
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Butyrates
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Integrin beta1
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Integrins
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NF-kappa B
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Protein-Tyrosine Kinases
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Focal Adhesion Kinase 1
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Focal Adhesion Protein-Tyrosine Kinases
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PTK2 protein, human
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AKT1 protein, human
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Sucrase
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CASP3 protein, human
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Caspase 3
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Caspases