Metabolism of 1'- and 4-hydroxymidazolam by glucuronide conjugation is largely mediated by UDP-glucuronosyltransferases 1A4, 2B4, and 2B7.
Midazolam undergoes oxidative hydroxylation by CYP3A to its metabolites, which are excreted mainly as glucuronidated conjugates into the urine. In this study, we examined the glucuronidation of hydroxymidazolam in human liver microsomes (HLMs) and characterized the UDP-glucuronosyltransferases (UGTs) involved in 1'- and 4-hydroxymidazolam glucuronidation. Among the 12 UGT isoforms tested, the O- and N-glucuronidation of 1'-hydroxymidazolam was mediated by UGT2B4/2B7 and 1A4, respectively. In contrast, the glucuronidation of 4-hydroxymidazolam was mediated by UGT1A4. Consistent with these observations, the UGT1A4 inhibitor hecogenin and the UGT2B7 substrate diclofenac potently inhibited the N- and O-glucuronidation of 1'-hydroxymidazolam in HLMs, respectively. A correlation analysis of UGT enzymatic activity and the formation rate of glucuronide metabolites from 1'- and 4-hydroxymidazolam in 25 HLMs showed that hydroxymidazolam glucuronidation is correlated with UGT1A4-mediated lamotrigine glucuronidation and UGT2B7-mediated diclofenac glucuronidation activity. Taken together, these findings indicate that UGT1A4, 2B4, and 2B7 are major isoforms responsible for glucuronide conjugate formation from 1'- and 4-hydroxymidazolam, which are the two major oxidative metabolites of midazolam.
Seo
Kyung-Ah
KA
Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Korea.
Bae
Soo Kyung
SK
Choi
Young-Kil
YK
Choi
Chang Soo
CS
Liu
Kwang-Hyeon
KH
Shin
Jae-Gook
JG
D002851:Chromatography, High Pressure Liquid; D020719:Glucuronides / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D050217:Metabolic Detoxication, Phase II; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D008874:Midazolam / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D011994:Recombinant Proteins / Q000378:metabolism; D053719:Tandem Mass Spectrometry
D020719:Glucuronides; D011994:Recombinant Proteins; C019787:bilirubin glucuronoside glucuronosyltransferase; C042940:4-hydroxymidazolam; C040081:1-hydroxymethylmidazolam; C491474:UGT2B7 protein, human; D014453:Glucuronosyltransferase; C486404:UGT2B4 protein, human; D008874:Midazolam