title: Induction of lactase biosynthesis in the human intestinal epithelial cell line Caco-2.
abstract: The human colonic adenocarcinoma cell line Caco-2 forms monolayers of differentiated enterocyte-like cells when cultured on permeable supports. After confluency, Caco-2 cells express a number of brush-border enzymes including lactase-phlorizin hydrolase, sucrase-isomaltase and dipeptidylpeptidase IV. We have studied, with particular emphasis on lactase-phlorizin hydrolase, the modulation of biosynthesis of these enzymes by stimulating second messenger systems. Forskolin induced lactase-phlorizin hydrolase synthesis approximately fourfold within 7 h, suppressed sucrase-isomaltase synthesis, and had little effect on dipeptidylpeptidase IV. Dibutyryl-cAMP, 8-bromo-cAMP and vasoactive intestinal peptide also increased lactase-phlorizin hydrolase biosynthesis, indicating c-AMP dependent regulation. The induction of lactase-phlorizin hydrolase biosynthesis could be inhibited by actinomycin D and was preceded by a fourfold increase in lactase-phlorizin hydrolase mRNA levels, suggesting transcriptional control. Phorbol 12-myristate 13-acetate had an inhibitory effect on brush-border enzyme synthesis, in particular on sucrase-isomaltase, and blocked the forskolin-induced biosynthesis of lactase-phlorizin hydrolase. Lactase-phlorizin hydrolase synthesis was also inducible by hydrocortisone, but maximal induction required at least 3 days during which time sucrase-isomaltase synthesis diminished. The results indicate opposite regulation of lactase-phlorizin hydrolase and sucrase-isomaltase via cAMP and corticosteroids, and suggest that the Caco-2 cell line can serve as a model system to study aspects of the humoral regulation of human intestinal brush-border enzymes in cell culture.
authors.affiliation: Department of Pharmacology, University of Basel, Switzerland.
authors.forename: H P
authors.initials: HP
authors.lastname: Hauri
authors.forename: B
authors.initials: B
authors.lastname: Sander
authors.forename: H
authors.initials: H
authors.lastname: Naim
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000230:Adenocarcinoma; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D003110:Colonic Neoplasms; D000242:Cyclic AMP / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D043322:Lactase; D010694:Lactase-Phlorizin Hydrolase / Q000096:biosynthesis; D008715:Methionine / Q000378:metabolism; D008871:Microvilli / Q000201:enzymology; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000302:isolation & purification
chemical_list: D003609:Dactinomycin; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D008715:Methionine; D000242:Cyclic AMP; D013394:Sucrase-Isomaltase Complex; D043322:Lactase; D001616:beta-Galactosidase; D010694:Lactase-Phlorizin Hydrolase; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine