Inactivation of CYP2D6 by methylenedioxymethamphetamine in different recombinant expression systems

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• 作者：Linh M. Van ; Judith. A. Hargreaves ; Martin S. Lennard ; Geoffrey T. Tucker ; Amin Rostami-Hodjegan
• 关键词：Different rCYPs in assessing mechanism-based inactivation ; Study design for mechanism-based inactivation ; CYP2D6 inactivation by Ecstasy (MDMA) ; Metabolic drug– ; drug interactions ; Enzyme kinetics ; Microsomal binding
• 刊名：European Journal of Pharmaceutical Sciences
• 出版年：2007
• 出版时间：September 2007
• 年：2007
• 卷：32
• 期：1
• 页码：8-16
• 全文大小：596 K

文摘

Recombinantly expressed CYP450 systems (rCYPs) are often used to screen for irreversible/quasi-irreversible enzyme inhibitors during drug development. The concentration- and time-dependent inactivation of CYP2D6 by methylenedioxymethamphetamine (MDMA) was compared in three different rCYP2D6 systems (yeast microsomes, Supersomes™ and Bactosomes™) under the conditions of the most commonly used protocols in assessing mechanism-based inactivation (MBI). MDMA (2–20 μM) was pre-incubated with enzyme for 0, 2.5 and 5 min followed by a five-fold dilution and further incubation with dextromethorpan (DEX) (50 μM). The formation of dextrorphan (DOR) from DEX was used as a specific marker of CYP2D6 activity. Concentration- and time-dependent inactivation of CYP2D6 by MDMA was observed with each rCYP system. However, the apparent kinetic parameters for MBI (k_inact, the maximum inactivation rate constant and K_I, the inhibitor concentration associated with half maximal rate of inactivation) were significantly greater (p < 0.05) for Bactosomes™ (0.95 ± 0.33 min⁻¹, 42.9 ± 20.1 μM) than those found using yeast microsomes (0.28 ± 0.04 min⁻¹, 2.86 ± 1.18 μM) and Supersomes™ (0.38 ± 0.05 min⁻¹, 3.66 ± 0.10 μM). After correction for depletion of MDMA during pre-incubation, k_inact and K_I values determined using Bactosomes™ decreased significantly but remained higher than for the other rCYP systems (p < 0.05). Substantial metabolism of DOR after its formation from DEX was also observed using Supersomes™ and Bactosomes™. Sub-optimal study design when investigating MBI may compromise the quantitative characterization of inhibitory characteristics using some rCYP systems.