Confirmation That Cytochrome P450 2C8 (CYP2C8) Plays a Minor Role in (S)-(+)- and (R)-(-)-Ibuprofen Hydroxylation in Vitro

Abstract

ABSTRACT:Various groups have sought to determine the impact of CYP2C8 genotype (and CYP2C8 inhibition) on the pharmacokinetics (PK) of ibuprofen (IBU) enantiomers. However, the contribution of cytochrome P450 2C8 (CYP2C8) in human liver microsomes (HLMs) has not been reported. Therefore, in vitro cytochrome P450 (P450) reaction phenotyping was conducted with selective inhibitors of cytochrome P450 2C9 (CYP2C9) and CYP2C8. In the presence of HLMs, sulfaphenazole (CYP2C9 inhibitor), and anti-CYP2C9 monoclonal antibodies (mAbs) inhibited (73-100%) the 2-and 3-hydroxylation of both IBU enantiomers (1 and 20 M). At a higher IBU concentration (500 M), the same inhibitors were less able to inhibit the 2-hydroxylation of There has been continued interest in the safety and ADME properties of cyclooxygenase inhibitors. This interest has extended to 2-(4-isobutylphenyl)propionic acid (ibuprofen, IBU), which is administered as a racemic mixture of (S)-(ϩ)-and (R)-(Ϫ)-enantiomers (Rodrigues, 2005;Agúndez et al., 2007;Pilotto et al., 2007;Blanco et al., 2008). The metabolism of both enantiomers is complex and involves direct (acyl) glucuronidation, 2-hydroxylation, and 3-hydroxylation (methyl hydroxylation) (Fig. 1). Once formed, the 3-hydroxy metabolite is converted almost completely to the corresponding carboxy derivative via cytosolic dehydrogenases (Rudy et al., 1991;Hamman et al., 1997;Davies, 1998). Only (R)-(Ϫ)-IBU undergoes (unidirectional) chiral inversion, which is significant because pharmacological activity after a racemic dose is attributed largely to the (S)-(ϩ)-enantiomer (Davies, 1998;Hao et al., 2005;Ding et al., 2007). Overall, it seems that P450-dependent metabolism accounts for approximately 70 and 30% of (S)-(ϩ)-IBU and (R)-(Ϫ)-IBU clearance, respectively (Rodrigues, 2005). At first glance, the pharmacokinetic profile of the latter is expected to be minimally affected by P450 inhibitors and genotype (e.g., CYP2C9*1/*3, CYP2C9*3/*3; CYP2C8*1/*3, CYP2C8*3/*3). (S)-(؉)-IBU (32-52%) and (R)-(؊)-IBU (30-64%), whereas the 3-hydroxylation of (S)-(؉)-IBU and (R)-(؊)-Currently available in vitro data show that CYP2C9 plays a major role (Ͼ70%) in the oxidative metabolism of racemic IBU and its individual enantiomers. However, hydroxylation of both enantiomers has also been measured with rCYP2C8 and other P450s (CYP3A4 and CYP2C19) (Leeman et al., 1993;Hamman et al., 1997;McGinnity et al., 2000). Such data have led various groups to conclude that both CYP2C forms catalyze the oxidative metabolism of IBU, and attempts have been made to evaluate the impact of both CYP2C9 and CYP2C8 genotype on the PK, pharmacodynamics, and side-effect profile of IBU enantiomers (Kirchheiner et al., 2002;Garcia-Martin et al., 2004; Martinez et al., 2005;Pilotto et al., 2007;Blanco et al., 2008). Clinical drug interaction studies with known inhibitors of CYP2C9 (e.g., fluconazole) and CYP2C8 (e.g., gemfibrozil) have been conducted also (Hynninen et al., 2006;Tornio et al., 2007).However, it is worth noting that CYP2C8-selective chemica...

Human Liver Expression of CYP2C8: Gender, Age, and Genotype Effects

“…A larger number of Niemi et al (2003) failed to see a difference in ibuprofen clearance in CYP2C8*1/*4 subjects (n ϭ 3) compared with CYP2C8*1/*1 subjects (n ϭ 19). However, this null result may be due to the fact that CYP2C8 may only play a minor role in the metabolism of ibuprofen, as determined in more recent in vitro studies (Chang et al, 2008).…”

Further Assessment of 17α-Ethinyl Estradiol as an Inhibitor of Different Human Cytochrome P450 Forms in Vitro

“…Perhaps the most important finding in the present study was the A, rates of MEL 6-OH formation were determined for a panel of rP450s (Ma et al, 2005). The contribution of each P450, defined as % TNR (% total nomalized rate), in HLM (B) and HIM (C) was determined as described by Chang et al (2008). Mean specific content for each P450 in HIM and HLM has been reported in the literature (Paine et al, 2006;Chang et al, 2008).…”

Dose of Phenobarbital and Age of Treatment at Early Life are Two Key Factors for the Persistent Induction of Cytochrome P450 Enzymes in Adult Mouse Liver

“…The enzyme activities of Cyp2b, Cyp2c, and Cyp3a in mouse microsomes were determined by ultra-performance liquid chromatography-quadrapole time of flight mass spectrometry (UPLC-QTOFMS) according to the previously established methods (Gustafson et al, 2005;Ma et al, 2007;Chang et al, 2008;Lam et al, 2010). The liver tissues were homogenized in ice-cold buffer (150 mM KCl and 250 mM sucrose in 100 mM phosphate buffer, pH 7.4).…”