Knockout (KO) of mouse Cyp3a genes increases the expression of hepatic CYP2C enzymes, which can metabolize triazolam, a typical substrate of human CYP3A. There is still marked formation of 1’-hydroxytriazolam in Cyp3a-KO (3aKO) mice after triazolam dosing. Here, we generated a new model of humanized CYP3A (hCYP3A) mice with a double-KO background of Cyp3a and Cyp2c genes (2c3aKO), and we examined the metabolic profiles of triazolam in wild-type (WT), 2c3aKO, and hCYP3A/2c3aKO mice in vitro and in vivo . In vitro studies using liver microsomes showed that the formation of 1’-hydroxytriazolam in 2c3aKO mice was less than 8% of that in WT mice. The formation rate of 1’-hydroxytriazolam in hCYP3A/2c3aKO mice was eightfold higher than that in 2c3aKO mice. In vivo studies showed that area under the curve (AUC) of 1’-hydroxytriazolam in 2c3aKO mice was less than 3% of that in WT mice. The AUC of 1’-hydroxytriazolam in hCYP3A/2c3aKO mice was sixfold higher than that in 2c3aKO mice. These results showed that formation of 1’-hydroxytriazolam was significantly decreased in 2c3aKO mice. Metabolic functions of human CYP3A enzymes were distinctly found in hCYP3A mice with the 2c3aKO background. Moreover, hCYP3A/2c3aKO mice treated with clobazam showed human CYP3A-mediated formation of desmethylclobazam and prolonged elimination of desmethylclobazam, which is found in poor metabolizers of CYP2C19. The novel hCYP3A mouse model without mouse Cyp2c and Cyp3a genes (hCYP3A/2c3aKO) is expected to be useful to evaluate human CYP3A-mediated metabolism in vivo . SIGNIFICANT STATEMENT Humanized CYP3A (hCYP3A/2c3aKO) mice with a background of double knockout (KO) for mouse Cyp2c and Cyp3a genes were generated. Although CYP2C enzymes played a compensatory role in the metabolism of triazolam to 1’-hydroxytriazolam in the previous hCYP3A/3aKO mice with Cyp2c genes, the novel hCYP3A/2c3aKO mice clearly showed functions of human CYP3A enzymes introduced by chromosome engineering technology.
小鼠 Cyp3a
基因敲除(KO)会增加肝脏 CYP2C 酶的表达量,而 CYP2C 酶可以代谢人类 CYP3A 的典型底物--
三唑仑。在服用
三唑仑后,Cyp3a-KO(3aKO)小鼠体内仍有明显的1'-羟基
三唑仑形成。在这里,我们生成了一种具有 Cyp3a 和 Cyp2c
基因双 KO(2c3aKO)背景的人源化 CYP3A(hCYP3A)小鼠新模型,并研究了
三唑仑在野生型(WT)、2c3aKO 和 hCYP3A/2c3aKO 小鼠体内和体外的代谢情况。使用肝脏微粒体进行的体外研究表明,2c3aKO 小鼠体内 1'-hydroxytriazolam 的形成率不到 WT 小鼠的 8%。hCYP3A/2c3aKO 小鼠体内 1'-hydroxytriazolam 的形成率是 2c3aKO 小鼠的八倍。体内研究表明,2c3aKO 小鼠体内 1'-hydroxytriazolam 的曲线下面积(AUC)不到 WT 小鼠的 3%。hCYP3A/2c3aKO 小鼠体内 1'-hydroxytriazolam 的 AUC 是 2c3aKO 小鼠的六倍。这些结果表明,在 2c3aKO 小鼠体内,1'-羟基
三唑仑的形成明显减少。在具有 2c3aKO 背景的 hCYP3A 小鼠中,人类 CYP3A 酶的代谢功能被明显发现。此外,hCYP3A/2c3aKO小鼠接受
氯巴扎姆治疗后,显示出人类CYP3A介导的去
甲基氯巴扎姆的形成和去
甲基氯巴扎姆消除时间的延长,这在CYP2C19代谢不良的小鼠中是可以发现的。没有小鼠 Cyp2c 和 Cyp3a
基因的新型 hCYP3A 小鼠模型(hCYP3A/2c3aKO)有望用于评估人类 CYP3A 介导的体内代谢。 重要声明 生成了以小鼠 Cyp2c 和 Cyp3a
基因双
基因敲除(KO)为背景的人源化 CYP3A(hCYP3A/2c3aKO)小鼠。虽然在以前的带有 Cyp2c
基因的 hCYP3A/3aKO 小鼠中,CYP2C 酶在将
三唑仑代谢为 1'-hydroxytriazolam 的过程中发挥了补偿作用,但新型 hCYP3A/2c3aKO 小鼠明确显示了通过染色体工程技术引入的人 CYP3A 酶的功能。