Abstract 600: Aldosterone-Dependent Transfer of microRNA-Containing Exosomes Between Endothelial and Smooth Muscles Cells.
Background: Aldosterone is a cardiovascular risk factor and recent research has demonstrated that aldosterone increases exocytosis from endothelial cells, which may be an important signalling mechanism. Exosomes are small extracellular particles that contribute to cell-to-cell communication. Once released from a host cell they can circulate in the blood and transfer their contents (e.g. miRNAs) to recipient cells. We aimed to examine the effect of aldosterone on: 1) exosome release from endothelial cells and 2) exosome trafficking of miRNA from endothelial cells to smooth muscle cells.
Methods and Results: Human coronary artery endothelial cells (HCAECs) were incubated with aldosterone (100nM) or vehicle for 1 or 18 hours. Exosomes were isolated from cell media via ultracentrifugation and then analyzed by nanoparticle-tracking (NanoSight). Aldosterone increased exosome concentration by 2.65-fold (1h; 19.1x1010 particles/mL) or 3.25-fold (18h; 28.6x1010 particles/mL) when compared to the time-point vehicle control (7.2x1010 and 8.8x1010 particles/mL, respectively). To test exosome paracrine trafficking, HCAECs were transfected with a c.elegans miRNA (cel-miR-39) and incubated adjacent to human coronary artery smooth muscle cells (HCASMCs) separated by a 0.4μm filter for 24 hour, with or without aldosterone. qRT-PCR analysis was used to measure cel-miR-39 expression in HCASMCs following incubation near transfected HCAECs, a confirmation of trafficking. Importantly, levels of cel-miR-39 in HCASMCs increased significantly (2.42±0.52 fold; p=0.02) in aldosterone-stimulated cells, compared to control. Blocking transcription with Dactinomycin had no effect on aldosterone-mediated trafficking (cel-miR-39 expression 2.07±0.61 fold; p>0.05). Finally, antagonizing the mineralocorticoid receptor (MR) with spironolactone had no effect on cel-miR-39 expression in HCASMCs (3.43±1.49 fold; p>0.05).
Conclusion: This study demonstrates that aldosterone increases exosome secretion from endothelial cells, leading to increased uptake of exosome-packaged microRNAs by smooth muscle cells, independent of transcription and the MR. Together, this represents a novel mechanism by which aldosterone contributes to vascular disease.
Author Disclosures: S. Robertson: None. E. Dababneh: None. C. Bursill: None.
- © 2014 by American Heart Association, Inc.