Discovery and implementation of transcriptional biomarkers of synthetic LXR agonists in peripheral blood cells

• Published in: Journal of translational medicine Vol. 6; no. 1; p. 59
• Main Authors: DiBlasio-Smith, Elizabeth A, Arai, Maya, Quinet, Elaine M, Evans, Mark J, Kornaga, Tad, Basso, Michael D, Chen, Liang, Feingold, Irene, Halpern, Anita R, Liu, Qiang-Yuan, Nambi, Ponnal, Savio, Dawn, Wang, Shuguang, Mounts, William M, Isler, Jennifer A, Slager, Anna M, Burczynski, Michael E, Dorner, Andrew J, LaVallie, Edward R
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 16.10.2008; BioMed Central; BMC
• Subjects: Administration, Oral; Animals; Anticholesteremic Agents - administration & dosage; Anticholesteremic Agents - pharmacology; ATP Binding Cassette Transporter 1; ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - metabolism; Biomarkers; Blood Cells - drug effects; Blood Cells - metabolism; DNA-Binding Proteins - agonists; Dose-Response Relationship, Drug; Gene Expression Regulation - drug effects; Humans; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; Liver X Receptors; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear - agonists; RNA, Messenger - genetics; RNA, Messenger - metabolism; Transcription, Genetic - drug effects
• ISSN: 1479-5876; 1479-5876
• DOI: 10.1186/1479-5876-6-59

LXRs (Liver X Receptor alpha and beta) are nuclear receptors that act as ligand-activated transcription factors. LXR activation causes upregulation of genes involved in reverse cholesterol transport (RCT), including ABCA1 and ABCG1 transporters, in macrophage and intestine. Anti-atherosclerotic effects of synthetic LXR agonists in murine models suggest clinical utility for such compounds. Blood markers of LXR agonist exposure/activity were sought to support clinical development of novel synthetic LXR modulators. Transcript levels of LXR target genes ABCA1 and ABCG1 were measured using quantitative reverse transcriptase/polymerase chain reaction assays (qRT-PCR) in peripheral blood from mice and rats (following a single oral dose) and monkeys (following 7 daily oral doses) of synthetic LXR agonists. LXRalpha, LXRbeta, ABCA1, and ABCG1 mRNA were measured by qRT-PCR in human peripheral blood mononuclear cells (PBMC), monocytes, T- and B-cells treated ex vivo with WAY-252623 (LXR-623), and protein levels in human PBMC were measured by Western blotting. ABCA1/G1 transcript levels in whole-blood RNA were measured using analytically validated assays in human subjects participating in a Phase 1 SAD (Single Ascending Dose) clinical study of LXR-623. A single oral dose of LXR agonists induced ABCA1 and ABCG1 transcription in rodent peripheral blood in a dose- and time-dependent manner. Induction of gene expression in rat peripheral blood correlated with spleen expression, suggesting LXR gene regulation in blood has the potential to function as a marker of tissue gene regulation. Transcriptional response to LXR agonist was confirmed in primates, where peripheral blood ABCA1 and ABCG1 levels increased in a dose-dependent manner following oral treatment with LXR-623. Human PBMC, monocytes, T- and B cells all expressed both LXRalpha and LXRbeta, and all cell types significantly increased ABCA1 and ABCG1 expression upon ex vivo LXR-623 treatment. Peripheral blood from a representative human subject receiving a single oral dose of LXR-623 showed significant time-dependent increases in ABCA1 and ABCG1 transcription. Peripheral blood cells express LXRalpha and LXRbeta, and respond to LXR agonist treatment by time- and dose-dependently inducing LXR target genes. Transcript levels of LXR target genes in peripheral blood are relevant and useful biological indicators for clinical development of synthetic LXR modulators.