title: Lumisterol is metabolized by CYP11A1: discovery of a new pathway.
abstract: Lumisterol3 (L3) is produced by photochemical transformation of 7-dehydrocholesterol (7-DHC) during exposure to high doses of ultraviolet B radiation. It has been assumed that L3 is biologically inactive and is not metabolized in the body. However, some synthetic derivatives of L3 display biological activity. The aim of this study was to test the ability of CYP11A1 to metabolize L3. Incubation of L3 with bovine or human CYP11A1 resulted in the formation of three major and a number of minor products. The catalytic efficiency of bovine CYP11A1 for metabolism of L3 dissolved in 2-hydroxypropyl-β-cyclodextrin was approximately 20% of that reported for vitamin D3 and cholesterol. The structures of the three major products were identified as 24-hydroxy-L3, 22-hydroxy-L3 and 20,22-dihydroxy-L3 by NMR. 22-Hydroxy-L3 was further metabolized by bovine CYP11A1 to 20,22-dihydroxy-L3. Both 22-hydroxy-L3 and 20,22-dihydroxy-L3 gave rise to a minor metabolite identified from authentic standard and mass spectrometry as pregnalumisterol (pL) (product of C20-C22 side chain cleavage of L3) and two trihydroxy-L3 products. The capability of tissues expressing CYP11A1 to metabolize L3 was demonstrated using pig adrenal fragments where 20,22-dihydroxy-L3, 22-hydroxy-L3, 24-hydroxy-L3 and pL were detected by LC/MS. Thus, we have established that L3 is metabolized by CYP11A1 to 22- and 24-hydroxy-L3 and 20,22-dihydroxy-L3 as major products, as well as to pL and other minor products. The previously reported biological activity of pL and the presence of CYP11A1 in skin suggest that this pathway may serve to produce biologically active products from L3, emphasizing a novel role of CYP11A1 in sterol metabolism.
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA, Australia. Electronic address: robert.tuckey@uwa.edu.au.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Tuckey
authors.affiliation: Department of Pathology and Laboratory Medicine, Center for Cancer Research, University of Tennessee Health Science Center, Memphis, TN, USA; Department of Medicine, Division of Rheumatology and Connective Tissue Diseases, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Andrzej T
authors.initials: AT
authors.lastname: Slominski
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Chloe Y S
authors.initials: CY
authors.lastname: Cheng
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA; Department of Pharmaceutical Sciences, School of Pharmacy, South College, Knoxville, TN, USA.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Pathology and Laboratory Medicine, Center for Cancer Research, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Tae-Kang
authors.initials: TK
authors.lastname: Kim
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Xiao
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004875:Ergosterol / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D053858:Metabolic Networks and Pathways; D008956:Models, Chemical; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D013552:Swine
chemical_list: D002786:Cholesterol Side-Chain Cleavage Enzyme; D004875:Ergosterol
keywords: CYP11A1; Cytochrome P450scc; Hydroxylation; Lumisterol; Vitamin D3