Received for publication September 12, 2007.
Revised December 18, 2007.
Accepted for publication December 18, 2007.

Induction of metabolism and transport in human intestine: Validation of precision-cut slices as a tool to study induction of drug metabolism in human intestine in vitro

Abstract

Induction of drug enzyme activity in the intestine can strongly determine plasma levels of drugs. It is therefore important to predict drug-drug interactions in human intestine in vitro. We evaluated the applicability of human intestinal precision-cut slices for induction studies in vitro. Morphological examination and intracellular ATP levels indicated tissue integrity up to 24 h of incubation, whereas in proximal jejunum slices, the metabolic rate towards most substrates remained at 40-50% of initial values. In colon slices, the P450 conversions were below the detection limit, but conjugation rates remained relatively constant during incubation. The inducibility of drug metabolizing enzymes and PGP was evaluated using prototypical inducers for five induction pathways. -Naphthoflavone (AhR ligand) induced CYP1A1 (132-fold in colon, 362-fold in proximal jejunum) and UGT1A6 mRNA (9.8-fold in colon, 3.2-fold in proximal jejunum). In proximal jejunum, rifampicin (PXR ligand) induced CYP3A4 (5.2-fold), CYP2B6 (2-fold) UGT1A6 (2.2-fold) and MDR1/ABCB1 mRNA (2.7-fold), whereas 6-hydroxytestosterone formation (CYP3A4) increased 2-fold. In colon, RIF induced UGT1A6 32-fold and MDR1 2.2-fold. Dexamethasone (GR and PXR ligand) induced CYP3A4 mRNA (3.5-fold) and activity (5-fold) in proximal jejunum. Phenobarbital (CAR activator) induced CYP3A4 (4.1-fold, only in jejunum), CYP2B6 (4.9-fold in colon, 2.3-fold in proximal jejunum) and MDR1/ABCB1 mRNA and CYP3A4 activity (2-fold only proximal jejunum). Quercetin (Nrf2 activator) induced UGT1A6 mRNA (6.7-fold in colon, 2.2-fold in proximal jejunum). In conclusion, this study shows that human intestinal precision-cut slices are useful to study induction of drug metabolising enzymes and transporters in the human intestine.

Key words: CYP induction, cytochrome P450 regulation, drug-drug interactions, enzyme induction, extrahepatic drug metabolism, in vitro-in vivo prediction, phase II drug metabolism