title: Cholesterol 25-hydroxylation activity of CYP3A.
abstract: To date, many studies have been conducted using 25-hydroxycholesterol, which is a potent regulator of lipid metabolism. However, the origins of this oxysterol have not been entirely elucidated. Cholesterol 25-hydroxylase is one of the enzymes responsible for the metabolism of 25-hydroxycholesterol, but the expression of this enzyme is very low in humans. This oxysterol is also synthesized by sterol 27-hydroxylase (CYP27A1) and cholesterol 24-hydroxylase(CYP46A1), but it is only a minor product of these enzymes. We now report that CYP3A synthesizes a significant amount of 25-hydroxycholesterol and may participate in the regulation of lipid metabolism. Induction of CYP3A by pregnenolone-16α-carbonitrile caused the accumulation of 25-hydroxycholesterol in a cell line derived from mouse liver. Furthermore, treatment of the cells with troleandomycin, a specific inhibitor of CYP3A, significantly reduced cellular 25-hydroxycholesterol concentrations. In cells that overexpressed human recombinant CYP3A4, the activity of cholesterol 25-hydroxylation was found to be higher than that of cholesterol 4β-hydroxylation, a known marker activity of CYP3A4. In addition, 25-hydroxycholesterol concentrations in normal human sera correlated positively with the levels of 4β-hydroxycholesterol (r = 0.650, P < 0.0001, n = 78), but did not significantly correlate with the levels of 27-hydroxycholesterol or 24S-hydroxycholesterol. These results demonstrate the significance of CYP3A on the production of 25-hydroxycholesterol.
authors.affiliation: Department of Gastroenterology, Center for Collaborative Research, Ibaraki 300-0395, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Honda
authors.forename: Teruo
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ikegami
authors.forename: Junichi
authors.initials: J
authors.lastname: Iwamoto
authors.forename: Tomomi
authors.initials: T
authors.lastname: Maeda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hirayama
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Saito
authors.forename: Tamio
authors.initials: T
authors.lastname: Teramoto
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Matsuzaki
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects*; D015870:Gene Expression; D022781:Hepatocytes / Q000166:cytology / Q000201:enzymology*; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D016133:Polymerase Chain Reaction; D011285:Pregnenolone Carbonitrile / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D013250:Steroid Hydroxylases; D014217:Troleandomycin / Q000494:pharmacology; D008565:Membrane Proteins
chemical_list: D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D006888:Hydroxycholesterols; D011285:Pregnenolone Carbonitrile; D012333:RNA, Messenger; D013250:Steroid Hydroxylases; D014217:Troleandomycin; C007997:25-hydroxycholesterol; C510163:CYP3A4 protein, human; C507384:cholesterol 25-hydroxylase; C496508:Cyp3a11 protein, mouse; D008565:Membrane Proteins