Stereoselective metabolism of carvedilol by the β-naphthoflavone- inducible enzyme in human intestinal epithelial Caco-2 cells

Treatment of Caco-2 cells with β-naphthoflavone (β-NF) and 1α,25-dihydroxyvitamin D₃ (VD₃) induces UDP-glucuronosyltransferases (UGTs) and cytochrome P450 (CYP) 3A4, respectively. In the present study, we evaluated the metabolism of carvedilol in β-NF- and VD₃-treated Caco-2 cells. The metabolism of R-carvedilol was not significant in non-treated Caco-2 cells, whereas S-carvedilol was significantly metabolized in the cells. The metabolism of R- and S-carvedilol was significantly increased by the treatment of Caco-2 cells with 50 μM β-NF for 3 d. In contrast, the treatment of Caco-2 cells with 250 nM VD₃ for 2 weeks did not induce a significant change in the metabolism of R- and S-carvedilol. The metabolism of carvedilol in β-NF-treated Caco-2 cells was markedly inhibited by a substrate of UGTs, baicalein. In addition, the expression of UGT1A1, 1A6, and 1A9 mRNA was increased in β-NF-treated Caco-2 cells as compared with non-treated cells. These findings indicated that carvedilol was metabolized stereoselectively by the β-NF-inducible enzyme in Caco-2 cells. The UGT1A subfamily in intestinal epithelial cells may be partly responsible for first-pass (presystemic) metabolism of the drug.