Selective Activation of Liver X Receptors by Acanthoic Acid-Related Diterpenes

Paqui G. Traves; Sonsoles Hortelano; Miriam Zeini; Ta-Hsiang Chao; Thanh Lam; Saskia T. Neuteboom; Emmanuel A. Theodorakis; Michael A. Palladino; Antonio Castrillo; Lisardo Bosca

doi:10.1124/mol.106.031906

Abstract

Terpenoids constitute a large family of natural steroids that are widely distributed in plants and insects. We investigated the effects of a series of diterpenes structurally related to acanthoic acid in macrophage functions. We found that diterpenes with different substitutions at the C4 position in ring A are potent activators of liver X receptors (LXRα and LXRβ) in both macrophage cell lines from human and mouse origin and primary murine macrophages. Activation of LXR by these diterpenes was evaluated in transient transfection assays and gene expression analysis of known LXR-target genes, including the cholesterol transporters ABCA1 and ABCG1, the sterol regulatory element-binding protein 1c, and the apoptosis inhibitor of macrophages (Spα). Moreover, active diterpenes greatly stimulated cholesterol efflux from macrophages. It is interesting that these diterpenes antagonize inflammatory gene expression mainly through LXR-dependent mechanisms, indicating that these compounds can activate both LXR activation and repression functions. Stimulation of macrophages with acanthoic acid diterpenes induced LXR-target gene expression and cholesterol efflux to similar levels observed with synthetic agonists 3-[3-[N-(2-chloro-3-trifluoromethylbenzyl)-(2,2-diphenylethyl)-amino]propyloxy]phenylacetic acid hydrochloride (GW3965) and N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)-ethyl]phenyl]-benzenesulfonamide [T1317 (T0901317)]. These effects observed in gene expression were deficient in macrophages lacking both LXR isoforms (LXRα,β^–/–). These results show the ability of certain acanthoic acid diterpenes to activate efficiently both LXRs and suggest that these compounds can exert beneficial effects from a cardiovascular standpoint through LXR-dependent mechanisms.

Footnotes

This work was supported by grants SAF2005-03022 from Ministerio de Educación Ciencia (MEC), ON03 180-02 from Fundacio la Caixa, and Fundacion Mutua Madrileña (to L.B.) and SAF2005-03270, Fundacio La Caixa BM05-228, Funcis 67/05, and the RyC program (to A.C.). P.G.T. and M.Z. were supported by grants from ISC-III, MEC, and Bancaja-Centro Nacional de Investigaciones Cardiovasculares.
A.C. and L.B. contributed equally to this work.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.106.031906.
ABBREVIATIONS: LXR, liver X receptor; DTP, diterpene; NOS-2, type-2 inducible nitric-oxide synthase; IL, interleukin; PPAR, peroxisome proliferator-activated receptor; TNF-α, tumor necrosis factor α; DMSO, dimethyl sulfoxide; WT, wild type; HEK, human embryonic kidney; DMEM, Dulbecco's modified Eagle's medium; CSF-1, colony-stimulating factor 1; PCR, polymerase chain reaction; RXR, retinoid X receptor; Dex, dexamethasone; RT-PCR, reverse transcription-polymerase chain reaction; TPA, 12-O-tetradecanoylphorbol-13-acetate; NFκB, nuclear factor κB; 58-035, 3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl]pro panamide; RANTES, regulated on activation normal T cell expressed and secreted; T1317 (T0901317), N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trifluoro-1-hydroxy-1(trifluoromethyl)-ethyl]phenyl]-benzenesulfonamide; GW3965, 3-[3-[N-(2-chloro-3-trifluoromethylbenzyl)-(2,2-diphenylethyl)amino]propyloxy]phenylacetic acid hydrochloride; AM580, 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)carboxamido]benzoic acid; LG268 (LG100268), 6-(1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)cyclopropyl)pyridine-3-carboxylic acid.
- Received October 18, 2006.
- Accepted February 28, 2007.