Interferon-stimulated gene 15 promotes cholesterol efflux by activating autophagy via the miR-17-5p/Beclin-1 pathway in THP-1 macrophage-derived foam cells

Macrophage autophagy contributes to the hydrolysis of cholesteryl ester into free cholesterol mainly for ATP-binding cassette transporter A1 (ABCA1)-dependent efflux. Interferon-stimulated gene 15 (ISG15) has been shown to regulate autophagy in multiple types of cells. The present study aimed to examine the effects of ISG15 on autophagy and cholesterol efflux in THP-1 macrophage-derived foam cells and to explore the underlying molecular mechanisms. Our results showed that overexpression of ISG15 promoted autophagy and cholesterol efflux and inhibited lipid accumulation without impact on ABCA1 expression. Inhibition of autophagy by 3-methyladenine (3-MA) abrogated the enhancing effects of ISG15 on cholesterol efflux. Both bioinformatics analysis and dual luciferase reporter assay identified Beclin-1 as a direct target of miR-17-5p. Moreover, ISG15 overexpression markedly decreased miR-17-5p levels and upregulated Beclin-1 expression. ISG15-induced enhancement of autophagy and cholesterol efflux was reversed by pretreatment with either miR-17-5p mimic or Beclin-1 siRNA. In conclusion, these findings suggest that ISG15 reduces miR-17-5p levels and thereby promotes Beclin-1-mediated autophagy, resulting in increased cholesterol efflux from THP-1 macrophage-derived foam cells.