180 Endothelial microparticles prevent lipid-induced endothelial dysfunction through activation of AKT/ENOS signalling pathway and attenuation of oxidative stress

Endothelial dysfunction is an early event in the pathogenesis of diabetes mellitus and its associated cardiovascular morbidities. Endothelial microparticles (EMPs) are endothelium-derived sub-micron vesicles that are released in response to diverse stimuli. Our study aims to investigate the effect of EMPs on endothelial cell function/dysfunction focusing on the Akt/eNOS signalling pathway and lipid-induced oxidative stress. EMPs were generated in vitro using TNFα-stimulated human umbilical vein endothelial cells (HUVECs). Flow cytometry was used to quantify the generated EMPs. HUVECs were cultured in M199 and treated with and without 100 µM palmitate in the presence or absence of 10 5 and 10 6 EMPs. Nitric oxide bioavailability in EMPs and HUVECs was measured using DAF-2. H 2 DCF-DA was used to quantify reactive oxygen species (ROS). Lipid peroxidation and activity of superoxide dismutase and catalase were determined by colorimetric assays, while RT-PCR and western blotting were used to assess eNOS, Akt and NOX4 expression. Analysis of the NO production suggests that EMPs carry a functional eNOS. Palmitate stimulation evoked oxidative stress and reduced activity of the antioxidant enzymes as well as A23187-stimulated NO production in HUVECs. RT-PCR and western blotting demonstrated a marked decrease in eNOS and Akt and increased NOX4 expression in palmitate-treated endothelial cells. EMPs protected against the palmitate-induced endothelial dysfunction through attenuation of oxidative stress and positive regulation of Akt/eNOS signalling, leading to an increased NO production. In conclusion, our data strongly suggest that EMPs express a functional eNOS and are effective in protecting endothelial cells against lipid-induced dysfunction.