Abstract 18555: Endothelial Microparticles Induced by TNF-α Vary in miRNA Content and Physical Properties: Implications for Their Role in Cell-to-Cell Communication
Introduction: Endothelial microparticles (EMPs) have traditionally been considered to be markers of inflammation and endothelial dysfunction; they have been shown to disrupt vascular homeostasis and contribute to the progression of atherosclerosis. However, the deleterious role of EMPs has recently been challenged by recent evidence suggesting that they may promote cell survival, stimulate endothelial cell (EC) regeneration and exert anti-inflammatory effects. Herein we aimed to further investigate physiologic and pathophysiologic mechanisms governing the role of EMPs in vascular homeostasis.
Hypothesis: Different populations of EMPs are produced in response to inflammation that are distinguished by their miRNA content and other physical properties.
Methods: Cultured ECs were treated with TNF-α plus or minus distinct EMP production pathway inhibitors for 24 hours. Released EMPs were characterized by flow cytometry (count, size, surface phosphatidylserine [PS] expression), scanning electron microscopy (size), Zetasizer (size and surface charge), and qRT-PCR (miRNA content). In a separate set of experiments EMPs were incubated with otherwise untreated ECs and apoptosis was assessed in these recipient cells by Caspase-3 activity.
Results: Through different signaling pathways, TNF-α-induced the release of distinct EMP populations. EMPs produced through the RhoA/Rho kinase (ROCK) pathway had 4-6 fold higher miRNA content, were less than 1 μm in size, had significantly less negative surface charge and 22.5% less available PS on their surface compared to EMPs generated through the caspase signaling pathway. Importantly, ROCK-dependent, miRNA-rich EMPs conveyed an anti-apoptotic message to recipient cells while miRNA-poor EMPs were highly pro-apoptotic (2-fold increase in Caspase-3 activity).
Conclusions: These findings are important because EMP-encapsulated miRNAs are likely to have a role in intercellular communication, but little is known about the biology of cell-to-cell transfer of miRNA. Our data provide insight into the previously reported conflicting atheroprotective and atherogenic roles of EMPs.
Author Disclosures: T. Alexy: None. K. Rooney: None. M. Weber: None. C.D. Searles: None.
- © 2014 by American Heart Association, Inc.