title: Hepatic bile acid metabolism and expression of cytochrome P450 and related enzymes are altered in Bsep (-/-) mice.
abstract: The bile salt export pump (BSEP/Bsep; gene symbol ABCB11/Abcb11) translocates bile salts across the hepatocyte canalicular membrane into bile in humans and mice. In humans, mutations in the ABCB11 gene cause a severe childhood liver disease known as progressive familial intrahepatic cholestasis type 2. Targeted inactivation of mouse Bsep produces milder persistent cholestasis due to detoxification of bile acids through hydroxylation and alternative transport pathways. The purpose of the present study was to determine whether functional expression of hepatic cytochrome P450 (CYP) and microsomal epoxide hydrolase (mEH) is altered by Bsep inactivation in mice and whether bile acids regulate CYP and mEH expression in Bsep (-/-) mice. CYP expression was determined by measuring protein levels of Cyp2b, Cyp2c and Cyp3a enzymes and CYP-mediated activities including lithocholic acid hydroxylation, testosterone hydroxylation and alkoxyresorufin O-dealkylation in hepatic microsomes prepared from female and male Bsep (-/-) mice fed a normal or cholic acid (CA)-enriched diet. The results indicated that hepatic lithocholic acid hydroxylation was catalyzed by Cyp3a/Cyp3a11 enzymes in Bsep (-/-) mice and that 3-ketocholanoic acid and murideoxycholic acid were major metabolites. CA feeding of Bsep (-/-) mice increased hepatic Cyp3a11 protein levels and Cyp3a11-mediated testosterone 2β-, 6β-, and 15β-hydroxylation activities, increased Cyp2b10 protein levels and Cyp2b10-mediated benzyloxyresorufin O-debenzylation activity, and elevated Cyp2c29 and mEH protein levels. We propose that bile acids upregulate expression of hepatic Cyp3a11, Cyp2b10, Cyp2c29 and mEH in Bsep (-/-) mice and that Cyp3a11 and multidrug resistance-1 P-glycoproteins (Mdr1a/1b) are vital components of two distinct pathways utilized by mouse hepatocytes to expel bile acids.
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T1Z3, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Hrycay
authors.forename: Dana
authors.initials: D
authors.lastname: Forrest
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Renxue
authors.initials: R
authors.lastname: Wang
authors.forename: Jenny
authors.initials: J
authors.lastname: Tai
authors.forename: Anand
authors.initials: A
authors.lastname: Deo
authors.forename: Victor
authors.initials: V
authors.lastname: Ling
authors.forename: Stelvio
authors.initials: S
authors.lastname: Bandiera
mesh_terms: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D019826:Cholic Acid / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004851:Epoxide Hydrolases / Q000378:metabolism; D005260:Female; D006900:Hydroxylation / Q000502:physiology; D008099:Liver / Q000201:enzymology* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; C490549:Abcb11 protein, mouse; D001647:Bile Acids and Salts; D003577:Cytochrome P-450 Enzyme System; D004851:Epoxide Hydrolases; D019826:Cholic Acid