Nuclear factor κB down-regulates human UDP-glucuronosyltransferase 1A1: a novel mechanism involved in inflammation-associated hyperbilirubinaemia.

Tzu-Yue Shiu, Tien-Yu Huang, Shih-Ming Huang, Yu-Lueng Shih, Heng-Cheng Chu, Wei-Kuo Chang, Tsai-Yuan Hsieh

Division of Gastroenterology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC.

The Biochemical journal 2013 Feb 1

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Jaundice or hyperbilirubinaemia is a common complication of sepsis. UGT1A1 (UDP-glucuronosyltransferase 1A1) is a critical gene for bilirubin metabolism and irinotecan detoxification. However, the molecular pathogenesis of hyperbilirubinaemia during inflammation needs to be further clarified. Human hepatic UGT1A1 expression was analysed by RT (reverse transcription)-PCR, qRT-PCR (quantitative real-time PCR) and Western blotting in response to LPS (lipopolysaccharide) stimulation. Transcription regulatory elements in the upstream promoter region of the human UGT1A1 gene were determined using EMSA (electrophoretic mobility-shift assay) and ChIP (chromatin immunoprecipitation). The important role of the transcription regulatory element was examined using a luciferase assay, and was determined by qRT-PCR using a transcription factor activation inhibitor. LPS down-regulated the UGT1A1 mRNA expression in human hepatoma cell lines. A newly identified NF-κB (nuclear factor κB)-binding site was located on the upstream promoter region (-725/-716) of the human UGT1A1 gene. LPS-induced NF-κB activation and specific binding to the NF-κB-binding site can suppress human UGT1A1 promoter activity and human UGT1A1 expression. We demonstrated that LPS mediates the suppression of human UGT1A1 expression through specific binding of NF-κB to this newly identified NF-κB-binding site in the upstream promoter of the human UGT1A1 gene. The present study may partly explain the molecular pathogenesis of inflammation-associated hyperbilirubinaemia.

Citation

Tzu-Yue Shiu, Tien-Yu Huang, Shih-Ming Huang, Yu-Lueng Shih, Heng-Cheng Chu, Wei-Kuo Chang, Tsai-Yuan Hsieh. Nuclear factor κB down-regulates human UDP-glucuronosyltransferase 1A1: a novel mechanism involved in inflammation-associated hyperbilirubinaemia. The Biochemical journal. 2013 Feb 1;449(3):761-70