TY - JOUR T1 - Up-Regulation of UDP-Glucuronosyltransferase (UGT) 1A4 by 17β-Estradiol: A Potential Mechanism of Increased Lamotrigine Elimination in Pregnancy JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1841 LP - 1847 DO - 10.1124/dmd.109.026609 VL - 37 IS - 9 AU - Huiqing Chen AU - Kyunghee Yang AU - Suyoung Choi AU - James H. Fischer AU - Hyunyoung Jeong Y1 - 2009/09/01 UR - http://dmd.aspetjournals.org/content/37/9/1841.abstract N2 - Oral clearance of lamotrigine, an antiepileptic drug commonly used in pregnant women, is increased in pregnancy by unknown mechanisms. In this study, we show that 17β-estradiol (E2) up-regulates expression of UDP glucuronosyltransferase (UGT) 1A4, the major enzyme responsible for elimination of lamotrigine. Endogenous mRNA expression levels of UGT1A4 in estrogen receptor (ER) α-negative HepG2 cells were induced 2.3-fold by E2 treatment in the presence of ERα expression. E2 enhanced transcriptional activity of UGT1A4 in a concentration-dependent manner in HepG2 cells when ERα was cotransfected. Induction of UGT1A4 transcriptional activity by E2 was also observed in ERα-positive MCF7 cells, which was abrogated by pretreatment with the antiestrogen fulvestrant (ICI 182,780). Analysis of UGT1A4 upstream regions using luciferase reporter assays identified a putative specificity protein-1 (Sp1) binding site (–1906 to –1901 base pairs) that is critical for the induction of UGT1A4 transcriptional activity by E2. Deletion of the Sp1 binding sequence abolished the UGT1A4 up-regulation by E2, and Sp1 bound to the putative Sp1 binding site as determined by a electrophoretic mobility shift assay. Analysis of ERα domains using ERα mutants revealed that the activation function (AF) 1 and AF2 domains but not the DNA binding domain of ERα are required for UGT1A4 induction by E2 in HepG2 cells. Finally, E2 treatment increased lamotrigine glucuronidation in ERα-transfected HepG2 cells. Together, our data indicate that up-regulation of UGT1A4 expression by E2 is mediated by both ERα and Sp1 and is a potential mechanism contributing to the enhanced elimination of lamotrigine in pregnancy. ER -