C24-hydroxylated stigmastane derivatives as Liver X Receptor agonists

• Published in: Chemistry and physics of lipids Vol. 212; pp. 44 - 50
• Main Authors: Castro Navas, Francisco Fermin, Giorgi, Gianluca, Maggioni, Daniela, Pacciarini, Manuela, Russo, Vincenzo, Marinozzi, Maura
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.05.2018
• Subjects: ATP Binding Cassette Transporter 1 - genetics; ATP Binding Cassette Transporter 1 - metabolism; Cell Line, Tumor; Crystallography, X-Ray; Humans; Ligands; Liver X Receptor; Liver X Receptors - antagonists & inhibitors; Liver X Receptors - metabolism; LXR; Molecular Conformation; Natural products; Oxysterols; Phytosterols; Protein Binding; Protein Isoforms - antagonists & inhibitors; Protein Isoforms - metabolism; Saringosterol; Stereoisomerism; Sterol Regulatory Element Binding Protein 1 - genetics; Sterol Regulatory Element Binding Protein 1 - metabolism; Stigmastane derivatives; Stigmasterol - analogs & derivatives; Stigmasterol - chemistry; Stigmasterol - metabolism; Stigmasterol - pharmacology; Transcriptome - drug effects; Stigmastane derivatives; Natural products; LXR; Phytosterols; Oxysterols; Saringosterol; Liver X Receptor
• ISSN: 0009-3084; 1873-2941
• DOI: 10.1016/j.chemphyslip.2018.01.005

•The efficient synthesis of four stigmastane derivatives, endowed with a hydroxyl group at C24 position, is described.•Absolute configuration of the newly created chiral centers was definitively assigned for all the four compounds by X-ray crystallography.•The ability of the two 24(S)-epimers, 10b and 11b, to interact with LXRs is reported.•Capability of 10a and 11a to induce the expression of LXR target genes ABCA1, SREBP1c, FASN, and SCD1 was demonstrated in U937 monocytic cell line. Phytosterols are stucturally correlated to the endogenous ligands of Liver X Receptor (LXR), a ligand-activated nuclear receptor that has emerged as an attractive drug target due to its ability to integrate metabolic and inflammatory signaling. Natural and semi-synthetic phytosterol derivatives characterized by the presence of side-chain oxygenated functions have shown to be able to modulate LXR activity. Here, we describe the efficient synthesis of four stigmastane derivatives, endowed with a hydroxyl group at C24 position, namely (24R)- and (24S)-stigmasta-5,28-diene-3β,24-ols (also referred to as saringosterols, 10a and 10b) and (24R)- and (24S)-stigmasta-5-ene-3β,24-ols (11a and 11b), starting from the readily available stigmasterol. Thanks to X-ray crystallography the absolute configuration of the newly created chiral centers was definitively assigned for all the four compounds. The subsequent luciferase assays with GAL-4 chimeric receptors evidenced the ability of the two 24(S)-epimers, 10b and 11b, to interact with LXRs, showing the same degree of affinity as (22R)-hydroxycholesterol (1). With regard to the isoform selectivity both the derivatives 10b and 11b showed a preference for LXRβ, up to 4-fold in terms of efficacy for 11b. The gene expression profiling of (24S)-stigmasta-5,28-diene-3β,24-ol (10a) and (24S)-stigmasta-5-ene-3β,24-ol (11a) demonstrated the capability of both the compounds to induce the expression of four well-known LXR target genes, such as ABCA1, SREBP1c, FASN, and SCD1 in U937 monocytic cell line, thus supporting the hypothesis they were LXR positive modulators.