Abstract
Endothelial microparticles (EMPs) are endothelium-derived submicron vesicles that are released in response to diverse stimuli and are elevated in cardiovascular disease, which is correlated with risk factors. This study investigates the effect of EMPs on endothelial cell function and dysfunction in a model of free fatty acid (FFA) palmitate-induced oxidative stress. EMPs were generated from TNF-α-stimulated HUVECs and quantified by using flow cytometry. HUVECs were treated with and without palmitate in the presence or absence of EMPs. EMPs were found to carry functional eNOS and to protect against oxidative stress by positively regulating eNOS/Akt signaling, which restored NO production, increased superoxide dismutase and catalase, and suppressed NADPH oxidase and reactive oxygen species (ROS) production, with the involvement of NF-erythroid 2-related factor 2 and heme oxygenase-1. Conversely, under normal conditions, EMPs reduced NO release and increased ROS and redox-sensitive marker expression. In addition, functional assays using EMP-treated mouse aortic rings that were performed under homeostatic conditions demonstrated a decline in endothelium-dependent vasodilatation, but restored the functional response under lipid-induced oxidative stress. These data indicate that EMPs harbor functional eNOS and potentially play a role in the feedback loop of damage and repair during homeostasis, but are also effective in protecting against FFA-induced oxidative stress; thus, EMP function is reflected by the microenvironment.—Mahmoud, A. M., Wilkinson, F. L., McCarthy, E. M., Moreno-Martinez, D., Langford-Smith, A., Romero, M., Duarte, J., Alexander, M. Y. Endothelial microparticles prevent lipid-induced endothelial damage via Akt/eNOS signaling and reduced oxidative stress.
Highlights
Endothelial microparticles (EMPs) are endothelium-derived submicron vesicles that are released in response to diverse stimuli and are elevated in cardiovascular disease, which is correlated with risk factors
The presence of peNOS in EMPs was further assessed by Western blot analysis using HUVECs as a control. peNOSSer1177 and total eNOS were detected in the EMP lysate (Fig. 1B)
NADPH oxidase activity as measured by lucigeninenhanced chemiluminescence (Fig. 5E) was significantly increased by both EMPs and palmitate, an effect that was more pronounced in the presence of palmitate; under palmitate-induced oxidative stress conditions, EMPs attenuated the effect, producing a significant decrease in the activity of NADPH oxidase compared with oxidative stress conditions alone (P, 0.001). This is the first report to demonstrate that EMPs restore the lipid-induced impairment of endothelium-dependent vasodilation and NO production. These data point to the possible involvement of Akt/eNOS and NF-erythroid 2–related factor 2 (Nrf2)/antioxidant response element (ARE) pathways in mediating the effects of EMPs on the endothelium
Summary
Endothelial microparticles (EMPs) are endothelium-derived submicron vesicles that are released in response to diverse stimuli and are elevated in cardiovascular disease, which is correlated with risk factors. ABBREVIATIONS: ACh, acetylcholine; ARE, antioxidant response element; BSA, bovine serum albumin; CAT, catalase; DAF-2, diaminofluorescein-2; EMP, endothelial microparticle; FFA, free fatty acid; HO-1, heme oxygenase-1; L-NAME, N-nitroarginine methyl ester; MDA, malondialdehyde; MP, microparticle; Nrf, NF-erythroid 2–related factor 2; NQO1, NAD(P)H:quinone oxido-reductase 1; ROS, reactive oxygen species; SOD, superoxide dismutase. Despite links with impaired endothelial function [28] and apoptosis [30], EMPs have been reported to protect endothelial cells against damage by promoting cell survival via induction of cytoprotective and antiinflammatory effects [17, 18, 31]
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