Endoplasmic Reticulum (ER) Stress-Generated Extracellular Vesicles (Microparticles) Self-Perpetuate ER Stress and Mediate Endothelial Cell Dysfunction Independently of Cell Survival

Abstract

Circulating extracellular vesicles (EVs) are recognized as biomarkers and effectors of endothelial dysfunction, the initiating step of cardiovascular abnormalities. Among these EVs, microparticles (MPs) are vesicles directly released from the cytoplasmic membrane of activated cells. MPs were shown to induce endothelial dysfunction through the activation of endoplasmic reticulum (ER) stress. However, it is not known whether ER stress can lead to MPs release from endothelial cells and what biological messages are carried by these MPs. Therefore, we aimed to assess the impact of ER stress on MPs shedding from endothelial cells, and to investigate their effects on endothelial cell function. EA.hy926 endothelial cells or human umbilical vein endothelial cells (HUVECs) were treated for 24 h with ER stress inducers, thapsigargin or dithiothreitol (DTT), in the presence or absence of 4-Phenylbutyric acid (PBA), a chemical chaperone to inhibit ER stress. Then, MPs were isolated and used to treat cells (10–20 μg/mL) for 24–48 h before assessing ER stress response, angiogenic capacity, nitric oxide (NO) release, autophagy and apoptosis. ER stress (thapsigargin or DDT)-generated MPs did not differ quantitatively from controls; however, they carried deleterious messages for endothelial function. Exposure of endothelial cells to ER stress-generated MPs increased mRNA and protein expression of key ER stress markers, indicating a vicious circle activation of ER stress. ER stress (thapsigargin)-generated MPs impaired the angiogenic capacity of HUVECs and reduced NO release, indicating an impaired endothelial function. While ER stress (thapsigargin)-generated MPs altered the release of inflammatory cytokines, they did not, however, affect autophagy or apoptosis in HUVECs. This work enhances the general understanding of the deleterious effects carried out by MPs in medical conditions where ER stress is sustainably activated such as diabetes and metabolic syndrome.

Role of Extracellular Vesicles in the Pathogenesis of Vascular Damage

“…30 Similarly, endoplasmic reticulum stressors (that mimic the effect of insulin resistance and high glucose on the endoplasmic reticulum) stimulate the release of large EVs, which reduce NO production in endothelial recipient cells. 32 Studies on animal models that mimic diabetesinduced endothelial dysfunction showed similar effect of circulating EVs on endothelial cells, although mediated by different mechanisms. Circulating EVs, collected from diabetic mice, display higher levels of Arg1 (arginase 1) than EVs from normoglycemic controls.…”

“…30 Similarly, endoplasmic reticulum stressors (that mimic the effect of insulin resistance and high glucose on the endoplasmic reticulum) stimulate the release of large EVs, which reduce NO production in endothelial recipient cells. 32…”

Extracellular Vesicles as Drivers of Immunoinflammation in Atherothrombosis

“…EVs of several cellular origins (mainly derived from ECs) upon distinct inflammatory stimuli (oxidized low-density lipoprotein (LDL), angiotensin II, hypertension, visceral adipose tissue, and infection) or isolated from diseased patients (circulating EVs) directly cause harmful effects on physiological EC function and vasorelaxation by impairing nitric oxide (NO) bioavailability via regulation of NO, nitric oxide synthase, nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase, and prostacyclin as well as reactive oxygen species (ROS) and endoplasmic reticulum stress [ 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ]. RBCs play key roles in vascular homeostasis.…”

FGF21 attenuates high uric acid‑induced endoplasmic reticulum stress, inflammation and vascular endothelial cell dysfunction by activating Sirt1

“…Activation of ER stress, which frequently occurs using diabetes and metabolic syndrome, can cause endothelial dysfunction ( 27 ). The eIF2A/ATF4/CHOP signaling pathway serves an important role in regulating ER stress ( 28 ).…”