Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg Str. 1, Hannover, Germany.
J Hepatol. 2010 Apr;52(4):570-8. doi: 10.1016/j.jhep.2010.01.010. Epub 2010 Feb 4.
BACKGROUND & AIMS: Cholestasis is a serious complication of many liver diseases leading to increased serum bile acids (BA) and their conjugates. Chenodeoxycholic (CDCA) acid is a substrate of the human hepatic UDP-glucuronosyltransferase (UGT) 1A3. UGT1A3 may, therefore, be a BA-inducible gene relevant to BA regulation.
BA and human bile were used to induce UGT1A3 in HepG2 cells. Genomic DNA was analyzed by PCR amplification and sequencing. Transcriptional regulation was studied by DNA mutagenesis, RT-PCR, luciferase reporter gene constructs and electrophoretic mobility shift assays (EMSA).
CDCA differentially induced UGT1A3 but not UGT1A4 expression. Bile from ursodeoxycholic acid (UDCA)-treated and untreated patients differentially induced UGT1A3. A farnesoid X receptor (FXR) half-site DNA motif was identified in the UGT1A3 5' upstream region. The FXR inducer GW4064 activated UGT1A3 transcription, and electrophoretic mobility shift assays identified UGT1A3 as a FXR target gene.
Transcriptional regulation of the human bile acid and xenobiotic UGT1A3 by its substrate CDCA and FXR is shown. CDCA glucuronidation can be controlled by feed back inhibition proceeding via the glucuronidation of CDCA. UDCA does not induce UGT1A3 transcription. Since UGT1A3 is significantly induced by xenobiotics this physiologically links xenobiotic and bile acid metabolism to cholestasis.
胆淤积是许多肝脏疾病的严重并发症，导致血清胆汁酸（BA）及其共轭物增加。鹅去氧胆酸（CDCA）是人类肝 UDP-葡糖醛酸基转移酶（UGT）1A3 的底物。因此，UGT1A3 可能是与 BA 调节相关的 BA 诱导基因。
用 BA 和人胆汁诱导 HepG2 细胞中的 UGT1A3。通过 PCR 扩增和测序分析基因组 DNA。通过 DNA 诱变、RT-PCR、荧光素酶报告基因构建体和电泳迁移率变动分析（EMSA）研究转录调控。
CDCA 差异诱导 UGT1A3 但不诱导 UGT1A4 表达。来自熊去氧胆酸（UDCA）治疗和未治疗患者的胆汁差异诱导 UGT1A3。在 UGT1A3 5'上游区域鉴定出法尼醇 X 受体（FXR）半位点 DNA 基序。FXR 诱导剂 GW4064 激活 UGT1A3 转录，电泳迁移率变动分析鉴定 UGT1A3 为 FXR 靶基因。
显示了人胆汁酸和外源性 UGT1A3 的转录调节，由其底物 CDCA 和 FXR 进行。CDCA 的葡萄糖醛酸化可以通过 CDCA 的葡萄糖醛酸化进行反馈抑制来控制。UDCA 不诱导 UGT1A3 转录。由于 UGT1A3 被外源性物质显著诱导，因此这在生理上将外源性物质和胆汁酸代谢与胆淤积联系起来。
