Nonsteroidal anti-inflammatory drugs and phenols glucuronidation in Caco-2cells - Identification of the UDP-glucuronosyltransferases UGT1A6, 1A3 and2B7

Glucuronidation of phenols (I-naphthol, 4-methylumbelliferone) and nonstero idal anti-inflammatory drugs (NSAIDs) such as ketoprofen, naproxen and carp rofen was investigated in human colon carcinoma Caco-2 cell clones. Glucuro nidation of these substances was highly effective in microsomes of the clon es PD-7 and TC-7, but much lower in the PF-11 clone. The activity increased up to a maximum after 21 days of culture. RT-PCR experiments indicated tha t the PD-7 and TC-7 clones expressed the UDP-glucuronosyltransferase (UGT) isoforms UGT1A6, UGT1A3 and UGT2B7, which could account for the glucuronida tion of phenols and carboxylic acids observed. beta-Naphthoflavone stimulat ed by 2-fold the enzyme activity toward l-naphthol in PD-7 and TC-7 clones, but not in PF-11 cells. This increase was parallel to that of the UGT1A6 m RNA level. Glucuronidation of ketoprofen was also sensitive to the inducing effect of beta-naphthoflavone. Actinomycin D and cycloheximide did not aff ect the induction of UGT1A6 by beta-naphthoflavone, but suppressed that of ketoprofen UGT. The UGT1A3 mRNA content was enhanced by beta-naphthoflavone ; by contrast, that of UGT2B7 was insensitive to the inducer. In conclusion , several UGT isoforms of both families 1 and 2, which glucuronidale phenol s and carboxylic NSAIDs, have been identified in Caco-2 cells. They are dif ferently sensitive to P-naphthoflavone, (C) 2000 Elsevier Science Inc. All rights reserved.