Regulation of human Caco-2 intestinal epithelial brush border enzyme activity by cyclic nucleotides.

Regulation of intestinal epithelial differentiation is critical to normal function, malignant transformation, and healing. However, the intracellular regulation of intestinal epithelial differentiation is incompletely understood. We studied the effects of intracellular cyclic AMP and cyclic GMP on brush border enzyme activity in the human Caco-2 intestinal epithelial cell using pharmacologic agonists and antagonists of cAMP and cGMP mediated pathways as probes. The stable cyclic nucleotide analogs dibutyryl cAMP and dibutyryl cGMP selectively decreased Caco-2 dipeptidyl dipeptidase specific activity while increasing alkaline phosphatase. The inhibitors of adenylate and guanylate cyclase KT5720 and KT5823 each exerted the opposite effects. Combinations of dibutyryl cAMP and dibutyryl cGMP demonstrated synergistic effects on each brush border enzyme but KT5720 and KT5823 were less than additive. Thus, cAMP and CGMP may regulate human intestinal epithelial differentiation by interacting pathways.