LXR-activating oxysterols induce the expression of inflammatory markers in endothelial cells through LXR-independent mechanisms

Fulvio Morello, Elisa Saglio, Alessio Noghero, Domenica Schiavone, Tracy Ann Williams, Andrea Verhovez, Federico Bussolino, Franco Veglio, Paolo Mulatero

Research output: Contribution to journalArticle

Abstract

Aims: Liver X receptors α and β (LXRα, LXRβ) are key regulators of cholesterol homeostasis. The effects of LXR ligands on endothelial cells are largely unknown. While oxysterol LXR agonists can increase the endothelial-leukocyte interaction, synthetic LXR agonists are anti-atherogenic and anti-inflammatory. Mechanistic differences may underlie such findings. Methods and results: LXRα and LXRβ were found to be expressed in human endothelial cells. While synthetic LXR agonists could blunt the LPS-induced up-regulation of adhesion molecules (ICAM-1, VCAM-1, E-Selectin), 22-hydroxycholesterol and 24,25-epoxycholesterol enhanced such response. Microarray profiling further showed that the endothelial gene expression fingerprints of 22-hydroxycholesterol and T0901317 largely differed and unexpectedly shared only a restricted number of genes. Indeed, 22-hydroxycholesterol down-regulated eNOS and up-regulated a vast cohort of inflammatory mediators such as adhesion molecules, cytokines, enzymes and transcription factors. Other LXR-activating oxysterols such as 24,25-epoxycholesterol, 25-hydroxycholesterol and 27-hydroxycholesterol could also stimulate the endothelial expression of inflammatory markers, although significant differences were observed. These effects persisted in LXR-silenced cells, confirming the mechanistic dissociation of oxysterol and LXR pathways. Furthermore, the oxysterol-induced expression of inflammatory markers was not secondary to cell apoptosis and may relate to oxidative stress. Conclusions: LXR-activating oxysterols comprehensively activate the expression of endothelial inflammation markers independently from LXRs. At proper dosage, synthetic LXR agonists are safe on endothelial cells and may even transrepress inflammatory reactions.

Original languageEnglish
Pages (from-to)38-44
Number of pages7
JournalAtherosclerosis
Volume207
Issue number1
DOIs
Publication statusPublished - Nov 2009

Keywords

  • Endothelium
  • Inflammation
  • LXR
  • Oxysterols

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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