title: LXRα is uniquely required for maximal reverse cholesterol transport and atheroprotection in ApoE-deficient mice.
abstract: The liver X receptor (LXR) signaling pathway is an important modulator of atherosclerosis, but the relative importance of the two LXRs in atheroprotection is incompletely understood. We show here that LXRα, the dominant LXR isotype expressed in liver, plays a particularly important role in whole-body sterol homeostasis. In the context of the ApoE(-/-) background, deletion of LXRα, but not LXRβ, led to prominent increases in atherosclerosis and peripheral cholesterol accumulation. However, combined loss of LXRα and LXRβ on the ApoE(-/-) background led to an even more severe cholesterol accumulation phenotype compared to LXRα(-/-)ApoE(-/-) mice, indicating that LXRβ does contribute to reverse cholesterol transport (RCT) but that this contribution is quantitatively less important than that of LXRα. Unexpectedly, macrophages did not appear to underlie the differential phenotype of LXRα(-/-)ApoE(-/-) and LXRβ(-/-)ApoE(-/-) mice, as in vitro assays revealed no difference in the efficiency of cholesterol efflux from isolated macrophages. By contrast, in vivo assays of RCT using exogenously labeled macrophages revealed a marked defect in fecal sterol efflux in LXRα(-/-)ApoE(-/-) mice. Mechanistically, this defect was linked to a specific requirement for LXRα(-/-) in the expression of hepatic LXR target genes involved in sterol transport and metabolism. These studies reveal a previously unrecognized requirement for hepatic LXRα for optimal reverse cholesterol transport in mice.
authors.affiliation: Howard Hughes Medical Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hong
authors.forename: Michele N
authors.initials: MN
authors.lastname: Bradley
authors.forename: Xin
authors.initials: X
authors.lastname: Rong
authors.forename: Xuping
authors.initials: X
authors.lastname: Wang
authors.forename: Alan
authors.initials: A
authors.lastname: Wagner
authors.forename: Victor
authors.initials: V
authors.lastname: Grijalva
authors.forename: Lawrence W
authors.initials: LW
authors.lastname: Castellani
authors.forename: Jon
authors.initials: J
authors.lastname: Salazar
authors.forename: Susan
authors.initials: S
authors.lastname: Realegeno
authors.forename: Rima
authors.initials: R
authors.lastname: Boyadjian
authors.forename: Alan M
authors.initials: AM
authors.lastname: Fogelman
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Van Lenten
authors.forename: Srinivasa T
authors.initials: ST
authors.lastname: Reddy
authors.forename: Aldons J
authors.initials: AJ
authors.lastname: Lusis
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Tangirala
authors.forename: Peter
authors.initials: P
authors.lastname: Tontonoz
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency*; D050197:Atherosclerosis / Q000378:metabolism* / Q000517:prevention & control*; D001692:Biological Transport; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D004198:Disease Susceptibility; D005786:Gene Expression Regulation; D008099:Liver / Q000378:metabolism; D000071518:Liver X Receptors; D008264:Macrophages / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D057093:Orphan Nuclear Receptors / Q000378:metabolism*; D010641:Phenotype
chemical_list: D001057:Apolipoproteins E; D000071518:Liver X Receptors; C000605214:Nr1h3 protein, mouse; D057093:Orphan Nuclear Receptors; D002784:Cholesterol