Characterization of ebastine, hydroxyebastine, and carebastine metabolism by human liver microsomes and expressed cytochrome P450 enzymes: major roles for CYP2J2 and CYP3A.
Ebastine undergoes extensive metabolism to form desalkylebastine and hydroxyebastine. Hydroxyebastine is subsequently metabolized to carebastine. Although CYP3A4 and CYP2J2 have been implicated in ebastine N-dealkylation and hydroxylation, the enzyme catalyzing the subsequent metabolic steps (conversion of hydroxyebastine to desalkylebastine and carebastine) have not been identified. Therefore, we used human liver microsomes (HLMs) and expressed cytochromes P450 (P450s) to characterize the metabolism of ebastine and that of its metabolites, hydroxyebastine and carebastine. In HLMs, ebastine was metabolized to desalkyl-, hydroxy-, and carebastine; hydroxyebastine to desalkyl- and carebastine; and carebastine to desalkylebastine. Of the 11 cDNA-expressed P450s, CYP3A4 was the main enzyme catalyzing the N-dealkylation of ebastine, hydroxyebastine, and carebastine to desalkylebastine [intrinsic clearance (CL(int)) = 0.44, 1.05, and 0.16 microl/min/pmol P450, respectively]. Ebastine and hydroxyebastine were also dealkylated to desalkylebastine to some extent by CYP3A5. Ebastine hydroxylation to hydroxyebastine is mainly mediated by CYP2J2 (0.45 microl/min/pmol P450; 22.5- and 7.5-fold higher than that for CYP3A4 and CYP3A5, respectively), whereas CYP2J2 and CYP3A4 contributed to the formation of carebastine from hydroxyebastine. These findings were supported by chemical inhibition and kinetic analysis studies in human liver microsomes. The CL(int) of hydroxyebastine was much higher than that of ebastine and carebastine, and carebastine was metabolically more stable than ebastine and hydroxyebastine. In conclusion, our data for the first time, to our knowledge, suggest that both CYP2J2 and CYP3A play important roles in ebastine sequential metabolism: dealkylation of ebastine and its metabolites is mainly catalyzed by CYP3A4, whereas the hydroxylation reactions are preferentially catalyzed by CYP2J2. The present data will be very useful to understand the pharmacokinetics and drug interaction of ebastine in vivo.
Liu
Kwang-Hyeon
KH
Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Gaegum-Dong, Busanjin-Gu, Busan, Korea.
Kim
Mi-Gyung
MG
Lee
Dong-Jun
DJ
Yoon
Yune-Jung
YJ
Kim
Min-Jung
MJ
Shon
Ji-Hong
JH
Choi
Chang Soo
CS
Choi
Young Kil
YK
Desta
Zeuresenay
Z
Shin
Jae-Gook
JG
D002090:Butyrophenones / Q000493:pharmacokinetics; D000090762:Cytochrome P-450 CYP2J2; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D006634:Histamine H1 Antagonists / Q000493:pharmacokinetics*; D006801:Humans; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D010105:Oxygenases / Q000096:biosynthesis*; D010880:Piperidines / Q000493:pharmacokinetics
D002090:Butyrophenones; C000717350:CYP2J2 protein, human; D006634:Histamine H1 Antagonists; D010880:Piperidines; C439605:hydroxyebastine; C058251:carebastine; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C104464:CYP3A protein, human; D000090762:Cytochrome P-450 CYP2J2; D051544:Cytochrome P-450 CYP3A; C058249:ebastine