Regulation of Cytochrome b5 Expression by miR-223 in Human Liver: Effects on Cytochrome P450 Activities

摘要

Purpose: Cytochrome b 5 (b 5) 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 b 5, the regulation of b 5 expression in human liver remains largely unknown. We investigated whether microRNA (miRNA) might be involved in the regulation of human b 5. 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 b 5. The miR-223 was overexpressed into HepG2 cells infected with adenovirus expressing human cytochrome P450. Results: In human livers, the b 5 protein levels were not positively correlated with the b 5 mRNA levels, and miR-223 levels were inversely correlated with the b 5 mRNA levels or the translational efficiencies. The luciferase assay showed that miR-223 functionally binds to the element in the 3′-untranslated region of b 5 mRNA. The overexpression of miR-223 significantly reduced the endogenous b 5 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 b 5 expression in the human liver, modulating P450 activities. © 2013 Springer Science+Business Media New York.