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

J Transl Med. 2008 Oct 16;6:59. doi: 10.1186/1479-5876-6-59.

Abstract

Background: 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.

Objective: Blood markers of LXR agonist exposure/activity were sought to support clinical development of novel synthetic LXR modulators.

Methods: 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.

Results: 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.

Conclusion: 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.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism
  • Administration, Oral
  • Animals
  • Anticholesteremic Agents / administration & dosage
  • Anticholesteremic Agents / pharmacology
  • 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
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Cytoplasmic and Nuclear / agonists*
  • Transcription, Genetic* / drug effects

Substances

  • ABCA1 protein, human
  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters
  • Anticholesteremic Agents
  • Biomarkers
  • DNA-Binding Proteins
  • Liver X Receptors
  • NR1H3 protein, human
  • Nr1h3 protein, mouse
  • Nr1h3 protein, rat
  • Orphan Nuclear Receptors
  • RNA, Messenger
  • Receptors, Cytoplasmic and Nuclear