College of Pharmacy, The Catholic University of Korea, Bucheon 420-743, Republic of Korea.
Chem Biol Interact. 2013 Sep 5;205(1):11-9. doi: 10.1016/j.cbi.2013.06.006. Epub 2013 Jun 15.
The present study was performed to evaluate the potency and specificity of sibutramine as an inhibitor of the activities of nine human CYP isoforms in liver microsomes. Using a cocktail assay, the effects of sibutramine on specific marker reactions of the nine CYP isoforms were measured in human liver microsomes. Sibutramine showed potent inhibition of CYP2B6-mediated bupropion 6-hydroxylation with an IC50 value of 1.61μM and Ki value of 0.466μM in a competitive manner at microsomal protein concentrations of 0.25mg/ml; this was 3.49-fold more potent than the typical CYP2B6 inhibitor thio-TEPA (Ki=1.59μM). In addition, sibutramine slightly inhibited CYP2C19 activity (Ki=16.6μM, noncompetitive inhibition) and CYP2D6 activity (Ki=15.7μM, noncompetitive inhibition). These observations indicated 35.6- and 33.7-fold decreases in inhibition potency, respectively, compared with that of CYP2B6 by sibutramine. However, no inhibition of CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, or CYP2E1 activities was observed. In addition, the CYP2B6 inhibitory potential of sibutramine was enhanced at a lower microsomal protein concentration of 0.05mg/ml. After 30min preincubation of human liver microsomes with sibutramine in the presence of NADPH, no shift in IC50 was observed in terms of inhibition of the activities of the nine CYPs, suggesting that sibutramine is not a time-dependent inactivator. These observations suggest that sibutramine is a selective and potent inhibitor of CYP2B6 in vitro, whereas inhibition of other CYPs is substantially lower. These in vitro data support the use of sibutramine as a well-known inhibitor of CYP2B6 for routine screening of P450 reversible inhibition when human liver microsomes are used as the enzyme source.
本研究旨在评估西布曲明作为肝微粒体中 9 种人细胞色素 CYP 同工酶活性抑制剂的效力和特异性。采用鸡尾酒测定法，在人肝微粒体中测量西布曲明对 9 种 CYP 同工酶特定标记反应的影响。西布曲明以竞争性方式在 0.25mg/ml 微粒体蛋白浓度下对 CYP2B6 介导的丁丙诺啡 6-羟化具有强烈的抑制作用，IC50 值为 1.61μM，Ki 值为 0.466μM；这比典型的 CYP2B6 抑制剂噻吩 TEPA（Ki=1.59μM）强 3.49 倍。此外，西布曲明轻度抑制 CYP2C19 活性（Ki=16.6μM，非竞争性抑制）和 CYP2D6 活性（Ki=15.7μM，非竞争性抑制）。与西布曲明相比，这些观察结果表明 CYP2B6 的抑制效力分别降低了 35.6 倍和 33.7 倍。然而，没有观察到对 CYP1A2、CYP2A6、CYP2C8、CYP2C9、CYP2D6 或 CYP2E1 活性的抑制。此外，在较低的 0.05mg/ml 微粒体蛋白浓度下，西布曲明的 CYP2B6 抑制潜力增强。在 NADPH 存在下，人肝微粒体中用西布曲明孵育 30min 后，9 种 CYP 活性抑制的 IC50 无变化，表明西布曲明不是时间依赖性失活剂。这些观察结果表明，西布曲明是 CYP2B6 的选择性和强效抑制剂，而对其他 CYP 的抑制作用要低得多。这些体外数据支持将西布曲明作为 CYP2B6 的已知抑制剂用于常规筛选人肝微粒体作为酶源时 P450 可逆抑制。
