Kamdem Landry K, Streit Frank, Zanger Ulrich M, Brockmöller Jürgen, Oellerich Michael, Armstrong Victor W, Wojnowski Leszek
Department of Clinical Pharmacology and Clinical Chemistry, Georg-August University, Goettingen, Germany.
Clin Chem. 2005 Aug;51(8):1374-81. doi: 10.1373/clinchem.2005.050047. Epub 2005 Jun 10.
Tacrolimus is metabolized predominantly to 13-O-demethyltacrolimus in the liver and intestine by cytochrome P450 3A (CYP3A). Patients with high concentrations of CYP3A5, a CYP3A isoenzyme polymorphically produced in these organs, require higher doses of tacrolimus, but the exact mechanism of this association is unknown.
cDNA-expressed CYP3A enzymes and a bank of human liver microsomes with known CYP3A4 and CYP3A5 content were used to investigate the contribution of CYP3A5 to the metabolism of tacrolimus to 13-O-demethyltacrolimus as quantified by liquid chromatography-tandem mass spectrometry.
Demethylation of tacrolimus to 13-O-demethyltacrolimus was the predominant clearance reaction. Calculated K(m) and V(max) values for CYP3A4, CYP3A5, and CYP3A7 cDNA-expressed microsomes were 1.5 micromol/L and 0.72 pmol x (pmol P450)(-1) x min(-1), 1.4 micromol/L and 1.1 pmol x (pmol P450)(-1) x min(-1), and 6 micromol/L and 0.084 pmol x (pmol P450)(-1) x min(-1), respectively. Recombinant CYP3A5 metabolized tacrolimus with a catalytic efficiency (V(max)/K(m)) that was 64% higher than that of CYP3A4. The contribution of CYP3A5 to 13-O-demethylation of tacrolimus in human liver microsomes varied from 1.5% to 40% (median, 18.8%). There was an inverse association between the contribution of CYP3A5 to 13-O-demethylation and the amount of 3A4 protein (r = 0.90; P <0.0001). Mean 13-O-demethylation clearances in CYP3A5 high and low expressers, estimated by the parallel-tube liver model, were 8.6 and 3.57 mL x min(-1) x (kg of body weight)(-1), respectively (P = 0.0088).
CYP3A5 affects metabolism of tacrolimus, thus explaining the association between CYP3A5 genotype and tacrolimus dosage. The importance of CYP3A5 status for tacrolimus clearance is also dependent on the concomitant CYP3A4 activity.
他克莫司在肝脏和肠道中主要通过细胞色素P450 3A(CYP3A)代谢为13 - O - 去甲基他克莫司。CYP3A5是在这些器官中多态性产生的一种CYP3A同工酶,CYP3A5浓度高的患者需要更高剂量的他克莫司,但这种关联的确切机制尚不清楚。
使用cDNA表达的CYP3A酶和一组已知CYP3A4和CYP3A5含量的人肝微粒体,通过液相色谱 - 串联质谱法定量研究CYP3A5对他克莫司代谢为13 - O - 去甲基他克莫司的贡献。
他克莫司去甲基化为13 - O - 去甲基他克莫司是主要的清除反应。CYP3A4、CYP3A5和CYP3A7 cDNA表达的微粒体的计算K(m)和V(max)值分别为1.5 μmol/L和0.72 pmol×(pmol P450)(-1)×min(-1)、1.4 μmol/L和1.1 pmol×(pmol P450)(-1)×min(-1)以及6 μmol/L和0.084 pmol×(pmol P450)(-1)×min(-1)。重组CYP3A5代谢他克莫司的催化效率(V(max)/K(m))比CYP3A4高64%。CYP3A5对人肝微粒体中他克莫司13 - O - 去甲基化的贡献在1.5%至40%之间(中位数为18.8%)。CYP3A5对13 - O - 去甲基化的贡献与3A4蛋白量之间呈负相关(r = 0.90;P <0.0001)。通过平行管肝脏模型估计,CYP3A5高表达者和低表达者的平均13 - O - 去甲基化清除率分别为8.6和3.57 mL×min(-1)×(kg体重)(-1)(P = 0.0088)。
CYP3A5影响他克莫司的代谢,从而解释了CYP3A5基因型与他克莫司剂量之间的关联。CYP3A5状态对他克莫司清除的重要性也取决于伴随的CYP3A4活性。