Abstract 11407: Ceramide-Induced Endothelial Microparticles Alter the Mechanism of Flow-Mediated Dilation
Endothelial microparticles (EMPs), small vesicles released from the endothelium, are known to be actively involved in cardiovascular disease. We recently reported that ceramide, a signaling lipid known to be elevated in patients with coronary artery disease (CAD), causes a transition in the mediator of flow-mediated dilation (FMD) from nitric oxide (NO) to mitochondrial-derived hydrogen peroxide (H2O2). We tested the hypothesis that ceramide is a stimulus for EMP formation, and that ceramide-induced EMPs alter the mechanism of FMD in human arterioles. Flow cytometry was utilized to identify and quantify EMPs from cultured human cardiac microvascular endothelial cells (HMVEC-C) treated with C2-Ceramide (5-50μM, 3hrs). A dose-response pattern was observed with 15μM producing the highest amount of CD31/Annexin V+ EMPs. Human adipose arterioles (100-200μm) from healthy patients were prepared for videomicroscopy, given EMPs intraluminally for 30 minutes, constricted with endothelin-1, and changes in internal diameter to flow were recorded. Maximal FMD was reduced in vessels treated with 500k EMPs/mL (41.4%±30.3 of maximal dilator capacity, n=4, p<0.01, one-way ANOVA*) compared to control (93.3%±2.0, n=4), whereas 250k EMPs/mL had no effect (91.9%±4.4, n=3). To determine if ceramide-induced EMPs alter the mechanism FMD, vasodilation was assessed in EMP-treated vessels (250k/mL) ± the nitric oxide synthase inhibitor L-NAME (100μM) or the hydrogen peroxide scavenger PEG-catalase (500U/mL). After EMP treatment, incubation with L-NAME had no effect on FMD (85.9%±9.8, n=3) compared to control (93.3%±2.0, n=4*); whereas PEG-catalase treatment eliminated dilation (maximal dilation -3.8, n=2). These data suggest that ceramide is not only capable of triggering EMP formation, but that ceramide-induced EMPs reduce dilation at high concentrations (500k/mL) and switch the mediator of dilation from NO to H2O2 at a lower concentration (250k/mL) where dilation is maintained. We conclude that ceramide-induced EMPs have a critical signaling role in the human microcirculation, and elucidation of these mechanisms may offer novel therapeutic targets for preserving tissue perfusion during disease.
- © 2013 by American Heart Association, Inc.