title: Hepatic expression of scavenger receptor class B type I (SR-BI) is a positive regulator of macrophage reverse cholesterol transport in vivo.
abstract: Hepatic expression of the scavenger receptor class B type I (SR-BI) promotes selective uptake of HDL cholesterol by the liver and is believed to play a role in the process of reverse cholesterol transport (RCT). We hypothesized that hepatic SR-BI expression is a regulator of the rate of integrated macrophage-to-feces RCT and used an in vivo model to test this hypothesis. Cholesterol-loaded and [3H]cholesterol-labeled J774 macrophages were injected intraperitoneally into mice, after which the appearance of the [3H]cholesterol in the plasma, liver, and feces over 48 hours was quantitated. Mice overexpressing SR-BI in the liver had significantly reduced [3H]cholesterol in the plasma but markedly increased [3H] tracer excretion in the feces over 48 hours. Conversely, mice deficient in SR-BI had significantly increased [3H]cholesterol in the plasma but markedly reduced [3H] tracer excretion in the feces over 48 hours. These studies demonstrate that hepatic SR-BI expression, despite its inverse effects on steady-state plasma HDL cholesterol concentrations, is an important positive regulator of the rate of macrophage RCT.
authors.affiliation: Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
authors.forename: YuZhen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jaqueline R
authors.initials: JR
authors.lastname: Da Silva
authors.forename: Muredach
authors.initials: M
authors.lastname: Reilly
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Billheimer
authors.forename: George H
authors.initials: GH
authors.lastname: Rothblat
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rader
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000235:genetics; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D008076:Cholesterol, HDL / Q000097:blood* / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D005243:Feces; D005260:Female; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D011849:Radioactive Tracers
chemical_list: D018955:CD36 Antigens; D008076:Cholesterol, HDL; D011849:Radioactive Tracers