5/6 nephrectomy (5/6Nx) effect on the liver. Mus musculus

Chronic renal failure (CRF) is associated with a decrease in drug metabolism. The present study investigated the repercussions of CRF on liver cytochrome P450 (CYPs), but the mechanisms have been little explored. On the other hand, the expression of several CYP genes exhibits circadian rhythm. Here we report that downregulation of hepatic CYP3A11 (the murine homolog to human CYP3A4; the most decrease in 5/6Nx using microarray analysis) by suppressing the expression of clock gene; D-site binding protein (DBP). In vivo experiments, the mRNA levels of hepatic CYP3A11 exhibit circadian rhythm regulated by DBP and E4BP4, and significantly decreased in 5/6Nx. Microarray analysis revealed that the general transcription factors of CYP3A11 did not changed. However, DBP were downregulated and several CYP genes controlled by DBP also significantly decreased in 5/6Nx. These downregulations were not observed in angiotensin II type 1alpha receptor (AT II R1a) deficient 5/6Nx because serum TGF-beta was not upregulate. In vitro experiments, the RNA levels of CYP3A11 and DBP were downregulated in wild-type mouse hepatocytes incubated with serum from 5/6Nx, but did not changed in Id2 (-/-) hepatocytes. In fact, hepatic Id2 was upregulated and caused the downregulation of DBP in 5/6Nx. Hepatocyte treated with SD208 (TGF-beta receptor 1 selectivity inhibitor) recovered CYP3A11, DBP and Id2 to control levels. Furthermore, 5/6Nx treated with tranilast (inhibitor of TGF-beta production or isolation) or candesartan (ARBs) also recovered CYP3A11 levels. Our findings define that DBP has effects on downregulation of CYP3A11. In CRF conditions, TGF-beta is upregulated by angiotensin II receptor in renal and downregulates DBP and CYP3A11 levels mediated by Id2 in liver. Furthermore, downregulation of CYP3A11 can prevent by tranilast or candesartan. Overall design: Differential gene expression between 5/6 nephrectomized and sham-operated mouse was measured on the liver.

慢性肾衰竭（Chronic renal failure, CRF）与药物代谢能力下降密切相关。本研究探讨了CRF对肝脏细胞色素P450（cytochrome P450, CYPs）的影响，但其相关机制鲜有研究。另一方面，多种CYP基因的表达呈现昼夜节律特征。本研究发现，肝脏CYP3A11（其为人类CYP3A4的小鼠同源基因；在5/6肾切除模型（5/6 nephrectomized, 5/6Nx）中经微阵列分析显示表达下调最为显著）的表达下调，是通过抑制时钟基因D位点结合蛋白（D-site binding protein, DBP）的表达实现的。
体内实验表明，肝脏CYP3A11的mRNA水平呈现由DBP和E4BP4调控的昼夜节律，且在5/6Nx模型中显著降低。微阵列分析显示，CYP3A11的通用转录因子并未发生表达变化。然而，DBP在5/6Nx模型中表达下调，且多种受DBP调控的CYP基因的表达也显著降低。
在血管紧张素II 1型α受体（angiotensin II type 1alpha receptor, AT II R1a）缺陷的5/6Nx模型中，未观察到上述下调现象，这是因为血清转化生长因子β（transforming growth factor-β, TGF-β）未出现上调。
体外实验中，用5/6Nx模型小鼠血清培养的野生型小鼠肝细胞内，CYP3A11和DBP的RNA水平均出现下调，但在Id2基因敲除（Id2 (-/-)）的肝细胞中未发生此类变化。事实上，在5/6Nx模型中，肝脏Id2的表达上调，进而导致DBP的表达下调。
用SD208（转化生长因子β受体1选择性抑制剂）处理肝细胞后，CYP3A11、DBP及Id2的表达均可恢复至对照水平。此外，对5/6Nx模型小鼠给予曲尼司特（tranilast，转化生长因子β生成或分泌抑制剂）或坎地沙坦（candesartan，血管紧张素Ⅱ受体拮抗剂，ARBs）干预，也可使CYP3A11的表达水平恢复正常。
本研究结果明确了DBP对CYP3A11表达下调的调控作用。在CRF状态下，血管紧张素Ⅱ受体介导肾脏中TGF-β的上调，进而通过肝脏中的Id2介导DBP及CYP3A11的表达下调。此外，曲尼司特或坎地沙坦可阻断CYP3A11的表达下调。
实验整体设计：本研究通过微阵列分析，检测了5/6肾切除小鼠与假手术（sham-operated）小鼠的肝脏组织基因表达差异。