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 sucraseisomaltase 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. Copyright © 1994, Wiley Blackwell. All rights reserved