Regulation of cytochrome b5 expression by miR-223 in human liver: effects on cytochrome P450 activities.
OBJECTIVE
Cytochrome b5 (b5) is a hemoprotein that transfers electrons to several enzymes to fulfill functions in fatty acid desaturation, methemoglobin reduction, steroidogenesis, and drug metabolism. Despite the importance of b5, the regulation of b5 expression in human liver remains largely unknown. We investigated whether microRNA (miRNA) might be involved in the regulation of human b5.


METHODS
Twenty-four human liver specimens were used for correlation analysis. In silico analysis and luciferase assay were performed to determine whether the predicted miRNAs functionally target to b5. The miR-223 was overexpressed into HepG2 cells infected with adenovirus expressing human cytochrome P450.


RESULTS
In human livers, the b5 protein levels were not positively correlated with the b5 mRNA levels, and miR-223 levels were inversely correlated with the b5 mRNA levels or the translational efficiencies. The luciferase assay showed that miR-223 functionally binds to the element in the 3′-untranslated region of b5 mRNA. The overexpression of miR-223 significantly reduced the endogenous b5 protein level and the mRNA stability in HepG2 cells. Moreover, the overexpression of miR-223 significantly reduced CYP3A4-catalyzed testosterone 6β-hydroxylation activity and CYP2E1-catalyzed chlorzoxazone 6-hydroxylase activity but not CYP1A2-catalyzed 7-ethoxyresorufin O-deethylase activity.


CONCLUSIONS
miR-223 down-regulates b5 expression in the human liver, modulating P450 activities.
Kei
K
Takahashi
Yuki
Y
Oda
Yasuyuki
Y
Toyoda
Tatsuki
T
Fukami
Tsuyoshi
T
Yokoi
Miki
M
Nakajima
D020413:3' Untranslated Regions; D001483:Base Sequence; D002460:Cell Line; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015786:Cytochromes b5 / Q000235:genetics*; D005786:Gene Expression Regulation; D056945:Hep G2 Cells; D006801:Humans; D006900:Hydroxylation; D008099:Liver / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013739:Testosterone / Q000378:metabolism
D020413:3' Untranslated Regions; D019388:Cytochrome P-450 CYP1A2; D019392:Cytochrome P-450 CYP2E1; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System; D015786:Cytochromes b5; D035683:MicroRNAs; D012333:RNA, Messenger; D013739:Testosterone; C525067:MIR223, human; C510163:CYP3A4 protein, human