Cigarette smoke extract induces CYP2B6 through constitutive androstane receptor in hepatocytes.
Smoking induces a wide range of drug-metabolizing enzymes. Among them, CYP2B6 as well as CYP1A2 is well known to be up-regulated in smokers. Although the induction of CYP1A2 is mediated by the aryl hydrocarbon receptor, the molecular mechanisms of CYP2B6 induction by smoking remain to be fully elucidated. In this study, by preparing cigarette smoke extract (CSE), we addressed the possibility that human constitutive androstane receptor (hCAR) is involved in smoking-mediated induction of CYP2B6. In HepG2 cells, CSE induced CYP1A2 but not CYP2B6, suggesting that CYP2B6 expression is differentially regulated from CYP1A2. Compared with liver in vivo, hCAR expression is dramatically reduced in cultured hepatocytes, such as HepG2. Therefore, to reconstitute hCAR signaling pathways in vitro, we generated adenovirus vector expressing hCAR. Real-time reverse transcription-polymerase chain reaction analyses revealed that the adenoviral transfection of hCAR resulted in the up-regulation of CYP2B6 mRNA, even in the absence of CSE. It is interesting to note that CSE stimulation augmented hCAR-mediated induction of CYP2B6. In contrast, the expression of CYP2B6 was not enhanced by adenovirus vector expressing β-galactosidase, a control vector, either in the presence or absence of CSE. In summary, hCAR mediated the CYP2B6 induction by CSE in Hep2G cells. These data suggest that smoking up-regulates CYP2B6 through hCAR in vivo.
Washio
Ikumi
I
Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.
Maeda
Makiko
M
Sugiura
Chika
C
Shiga
Ryota
R
Yoshida
Mitsuhiro
M
Nonen
Shinpei
S
Fujio
Yasushi
Y
Azuma
Junichi
J
D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D002478:Cells, Cultured; D000090702:Constitutive Androstane Receptor; D019388:Cytochrome P-450 CYP1A2 / Q000187:drug effects*; D065702:Cytochrome P-450 CYP2B6; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004790:Enzyme Induction; D057809:HEK293 Cells; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D012906:Smoke; D012907:Smoking / Q000378:metabolism*; D014026:Nicotiana; D015854:Up-Regulation
D000090702:Constitutive Androstane Receptor; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D018160:Receptors, Cytoplasmic and Nuclear; D012906:Smoke; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D019388:Cytochrome P-450 CYP1A2; D065702:Cytochrome P-450 CYP2B6; D010089:Oxidoreductases, N-Demethylating