Laboratory of Clinical Pharmaceutics, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe 650-8586, Japan.
Biol Pharm Bull. 2009 Dec;32(12):2046-52. doi: 10.1248/bpb.32.2046.
Hepatic metabolism is altered in some clinical conditions owing to the changes in the expression of metabolic enzymes and transporters. Therefore, we think that investigating the altered expression of metabolic enzymes and transporters is of particular significance to studies on drug disposition in some clinical conditions. We also believe that a simultaneous in vivo investigation of all factors affecting nuclear receptors and regulated genes is important to understand the relationship between nuclear receptors and their target genes. In this study, we induced cholestasis in rats by bile duct ligation (BDL), and investigated the changes in the mRNA expression of metabolic enzymes, transporters, and nuclear receptors and the protein levels of nuclear receptors in the nucleus by reverse transcriptase-polymerase chain reaction and Western blotting. In the liver of the rats subjected to BDL, the mRNA expression levels of cytochrome P450, conjugation enzymes, and transporters were concomitantly altered. The altered mRNA and protein levels of constitutive androstane receptor (CAR) and peroxisome proliferator-activated receptor alpha (PPARalpha) in the nucleus were consistent with the changes in the plasma concentrations of total and conjugated bilirubin and fatty acid, respectively. The mRNA expression of CAR and PPARalpha was linearly associated with the expression of the corresponding target genes. These results suggested that the increase in the levels of bilirubin and fatty acid on the BDL groups altered the mRNA and protein levels of CAR and PPARalpha, respectively in the nucleus, and this in turn altered the mRNA expression of metabolic enzymes and transporters as a hepatoprotective mechanism.
在某些临床情况下，由于代谢酶和转运体的表达变化，肝脏代谢会发生改变。因此，我们认为研究代谢酶和转运体的改变表达对于某些临床情况下的药物处置研究具有特殊意义。我们还认为，同时对影响核受体和调节基因的所有因素进行体内研究对于理解核受体与其靶基因之间的关系非常重要。在本研究中，我们通过胆管结扎（BDL）诱导大鼠胆汁淤积，并通过逆转录-聚合酶链反应和 Western 印迹法研究代谢酶、转运体和核受体的 mRNA 表达变化以及核受体的蛋白水平。在接受 BDL 的大鼠肝脏中，细胞色素 P450、结合酶和转运体的 mRNA 表达水平同时发生改变。核内组成型雄烷受体（CAR）和过氧化物酶体增殖物激活受体α（PPARα）的改变的 mRNA 和蛋白水平与总胆红素和结合胆红素以及脂肪酸的血浆浓度变化分别一致。CAR 和 PPARα 的 mRNA 表达与相应靶基因的表达呈线性相关。这些结果表明，BDL 组胆红素和脂肪酸水平的升高分别改变了核内 CAR 和 PPARα 的 mRNA 和蛋白水平，进而改变了代谢酶和转运体的 mRNA 表达，作为一种肝保护机制。
