Identification of the Udp-Glucuronosyltransferase Isoforms Involved in Mycophenolic Acid Phase Ii Metabolism

Abstract

ABSTRACT:Mycophenolic acid (MPA), the active metabolite of the immunosuppressant mycophenolate mofetil is primarily metabolized by glucuronidation. The nature of UDP-glucuronosyltransferases (UGTs) involved in this pathway is still debated. The present study aimed at identifying unambiguously the UGT isoforms involved in the production of MPA-phenyl-glucuronide (MPAG) and MPA-acylglucuronide (AcMPAG). A liquid chromatography-tandem mass spectrometry method allowing the identification and determination of the metabolites of mycophenolic acid was developed. The metabolites were characterized in urine and plasma samples from renal transplant patients under mycophenolate mofetil therapy and in vitro after incubation of mycophenolic acid with human liver (HLM), kidney (HKM), or intestinal microsomes (HIM). The UGT isoforms involved in MPAG or AcMPAG production were investigated using induced rat liver microsomes, heterologously expressed UGT (Supersomes), and chemical-selective inhibition of HLM, HKM, and HIM. The three microsomal preparations produced MPAG, AcMPAG, and two mycophenolate glucosides. Among the 10 UGT isoforms tested, UGT 1A9 was the most efficient for MPAG synthesis with a K m of 0.16 mM, close to that observed for HLM (0.18 mM). According to the chemical inhibition experiments, UGT 1A9 is apparently responsible for 55%, 75%, and 50% of MPAG production by the liver, kidney, and intestinal mucosa, respectively. Although UGT 2B7 was the only isoform producing AcMPAG in a significant amount, the selective inhibitor azidothymidine only moderately reduced this production (approximately ؊25%). In conclusion, UGT 1A9 and 2B7 were clearly identified as the main UGT isoforms involved in mycophenolic acid glucuronidation, presumably due to their high hepatic and renal expression.

De Novo Donor-Specific HLA Antibody Formation in Two Patients With Crigler-Najjar Syndrome Type I Following Human Hepatocyte Transplantation With Partial Hepatectomy Preconditioning

“…First, he presented on day 7 with mycophenolate intoxication. Mycophenolate is primarily metabolized by glucuronidation by UGT1A9 and UGT2B7 but not UGT1A1 17; however, accumulation of mycophenolate is explained by the mutation involving exon 4 of the UGT1A1 gene and thus affecting all UGT1A isoforms 18. Second, 6 mo after transplantation, patient 1 presented with crusted scabies ( Scabies norvegica ) infection, a particularly severe form found in immune‐compromised patients.…”

Effects of Herbal Supplements on Drug Glucuronidation. Review of Clinical, Animal, andIn VitroStudies

“…Inhibition of intestinal glucuronidation was 4-to 12-fold more potent than hepatic glucuronidation. MPA is an immunosuppressive drug that is metabolized in the liver by UGT1A9 and in the intestine by UGT1A7, 1A8, 1A9, and 1A10 [70][71][72]. In HLM, IC 50 values for inhibition by quercetin and kaempferol were 19.1 and 23 µM which are many fold higher than the expected plasma C max of flavonoids [52].…”

Lack of Association between Common Polymorphisms in UGT1A9 and Gene Expression and Activity

“…UGT1A9, a member of the UGT1A family, plays an important role in the glucuronidation of flavopiridol (Hagenauer et al, 2001;Ramirez et al, 2002), mycophenolic acid (Mackenzie 2000;Basu et al, 2004;Bernard and Guillemette, 2004;Miles et al, 2005;Picard et al, 2005), propofol (Court, 2005), acetaminophen (Court et al, 2001) and propranolol (Sten et al, 2006). UGT1A9 is expressed in multiple tissues, including liver, kidney, colon, and esophagus (Albert et al, 1999;Tukey and Strassburg, 2000).…”