MicroRNA-10a enrichment in factor VIIa–released endothelial extracellular vesicles: potential mechanisms

Abstract

BackgroundFactor VIIa induces the release of extracellular vesicles (EVs) from endothelial cells (EEVs). Factor VIIa–released EEVs are enriched with microRNA-10a (miR10a) and elicit miR10a-dependent cytoprotective responses. ObjectivesTo investigate mechanisms by which FVIIa induces miR10a expression in endothelial cells and sorts miR10a into the EVs. MethodsActivation of Elk-1 and TWIST1 expression was analyzed by immunofluorescence microscopy and immunoblot analysis. Small interfering RNA silencing approach was used to knock down the expression of specific genes in endothelial cells. EVs secreted from endothelial cells or released into circulation in mice were isolated by centrifugation and quantified by nanoparticle tracking analysis. Factor VIIa or EVs were injected into mice; mice were challenged with lipopolysaccharides to assess the cytoprotective effects of FVIIa or EVs. ResultsFVIIa activation of ERK1/2 triggered the activation of Elk-1, which led to the induction of TWIST1, a key transcription factor involved in miR10a expression. Factor VIIa also induced the expression of La, a small RNA-binding protein. Factor VIIa–driven acid sphingomyelinase (ASM) activation and the subsequent activation of the S1P receptor pathway were responsible for the induction of La. Silencing of ASM or La significantly reduced miR10a levels in FVIIa-released EEVs without affecting the cellular expression of miR10a. Factor VIIa–EEVs from ASM knocked-down cells failed to provide cytoprotective responses in cell and murine model systems. Administration of FVIIa protected wild-type but not ASM−/− mice against lipopolysaccharide-induced inflammation and vascular leakage. ConclusionOur data suggest that enhanced cellular expression of miR10a coupled with La-dependent sorting of miR10a is responsible for enriching FVIIa-released EVs with miR10a.