Objectives: Mycophenolate mofetil is a first-line drug after organ transplant, but there are differences in metabolism of mycophenolate mofetil among individuals. The UDP glucuronosyltransferase enzyme is the key metabolic enzyme for mycophenolate mofetil, and UGT1A8 gene polymorphisms may affect the elimination of mycophenolate mofetil in patients. Here, we conducted an in vitro study to explore the relation between UGT1A8 gene polymorphisms and mycophenolate mofetil metabolism.
Materials and methods: Five mutant loci overexpression vectors (UGT1A8 128C>T, 157C>A, 431C>T, 518C>G, and 830G>A) were constructed by genetic recombination and site-directed mutagenesis. We used Lipo2000 (Invitrogen, Carlsbad, CA, USA) to transfect the vectors into HEK293 cells. Mycophenolic acid, the active ingredient of mycophenolate mofetil, was added to different groups of cells. We then used the liquid chromatography tandem-mass spectrometry technique to detect production of the metabolite 7-O-mycophenolic acid glucuronide and to evaluate activity of the UDP glucuronosyltransferase enzyme in cells with different overexpression vectors.
Results: Mutations of UGT1A8 157C>A and 518C>G vectors can lead to increased activity of UDP glucuronosyltransferase enzymes and increased production of the 7-O-mycophenolic acid glucuronide metabolite, which showed 116% (P < .001) and 107% (P = .0191) production changes of 157C>A and 518C>G mutations, respectively, relative to wild-type UGT1A8. However, mutations of UGT1A8 431C>T and 830G>A loci resulted in decreased activity of UDP glucuronosyltransferase enzymes and decreased production of the metabolite, respectively showing 62.9% (P < .001) and 9.05% (P < .001) activity relative to wild-type UGT1A8. UGT1A8 128C>T had little effect on enzyme activity, with 96.8% activity relative to wild-type UGT1A8 (P = .0569).
Conclusions: Our results showed that UGT1A8 gene polymorphisms can affect the activity of UDP glucuronosyltransferase enzyme, which may influence the elimination of mycophenolate mofetil in different patients.