Endothelial extracellular vesicles modulate the macrophage phenotype: Potential implications in atherosclerosis

Abstract

Endothelial cells (ECs) and macrophages engage in tight and specific interactions that play critical roles in cardiovascular homeostasis and the pathogenesis of atherosclerosis. Extracellular vesicles (EVs) are circular membrane fragments released from the endosomal compartment as exosomes or shed from the surfaces of the membranes of most cell types. Increasing evidence indicates that EVs play a pivotal role in cell-to-cell communication. However, the contribution of EVs, as determine by oxidized low-density lipoprotein (ox-LDL)-exposed and/or Kruppel-like factor 2 (KLF2)-transduced ECs in the interaction between vascular ECs and monocytes/macrophages, which is a key event in atherosclerotic plaque development, has remained elusive. This study demonstrates the characteristic impact of EVs from ox-LDL-treated and/or KLF2-transduced ECs on the monocyte/macrophage phenotype in vitro and in vivo.Q-PCR showed that both the atherosclerosis inducer ox-LDL and atheroprotective factor KLF2 regulated inflammation-associated microRNA-155 (miR-155) expression in human umbilical vein endothelial cells (HUVECs). Moreover, coculture, immunofluorescence and flow cytometry revealed that miR-155 was enriched in ox-LDL-induced ECs-EVs and subsequently transferred to human monocytic THP1 cells, in which these vesicles enhance monocyte activation by shifting the monocytes/macrophages balance from anti-inflammatory M2 macrophages towards proinflammatory M1 macrophages; EVs from KLF2-expressing ECs suppressed monocyte activation by enhancing immunomodulatory responses and diminishing proinflammatory responses, which indicate the potent anti-inflammatory activities of these cells. Furthermore, oil red staining showed that atherosclerotic lesions were reduced in mice that received EVs from KLF2-transduced ECs with decreased proinflammatory M1 macrophages and increased anti-inflammatory M2 macrophages, and this effect is at least partly due to the decreased expression of inflammation-associated miR-155, confirming our in vitro findings. In summary, this study provides novel insights into the pathophysiological effects of altered EV secretion and/or microRNA content and their influence on modulating monocyte activation depending on the environment surrounding EVs-releasing ECs.

Part One: Extracellular Vesicles as Valuable Players in Diabetic Cardiovascular Diseases

“…EVs also play a key role in the cross talk between ECs and macrophages that can either act in the direction of vascular homeostasis or promote atherosclerosis, depending on their composition. It was shown that EVs secreted by Kruppel-like factor 2-treated ECs show anti-inflammatory actions, while oxidized-LDLtreated ECs produce EVs with high levels of miR-155, directing macrophage differentiation toward pro-inflammatory M1 macrophages [54]. In M1, but not in M2 macrophages, the inflammasome is known to be activated [55] and the inflammasome signaling leads to the secretion of pro-inflammatory exosomes [56], further favoring atherosclerosis progression.…”

Exosome and Macrophage Crosstalk in Sleep-Disordered Breathing-Induced Metabolic Dysfunction

“…It is also reported that inflammatory stroke can induce extracellular vesicles macrophage activation [ 179 ], and these EVs can act as messengers of macrophages sensing atherogenic stimuli [ 180 ]. Furthermore, endothelial EVs can modulate the macrophage phenotype with potential implications to atherosclerosis in patients [ 181 ]. Conversely, macrophage-derived exosomes induce inflammatory factors in endothelial cells under hypertensive conditions [ 182 ], while macrophage-secreted exosomes can deliver an miRNA-21 inhibitor to regulate BGC-823 cell proliferation of gastric cancer cells [ 183 ].…”

Senescent Microvesicles: A Novel Advance in Molecular Mechanisms of Atherosclerotic Calcification

“…It is well known that atherosclerosis, the hallmark sign of CVDs, is caused by dyslipidaemia and some studies have shown the role of EVs in the different stages of atherosclerosis [ 7 , 20 , 21 , 22 ]. Moreover, the number and phenotype of MVs have been associated with major cardiovascular risk factors such as smoking, diabetes mellitus, obesity, HT, dyslipidaemia and metabolic syndrome [ 19 ].…”

“…Recently, MVs have emerged as new regulators of biological functions in atherothrombosis [ 19 ]. MVs produce inflammatory effects, cell proliferation, thrombosis and calcification in the vasculature and appear to in human atherosclerotic plaques [ 7 , 20 , 21 , 22 ]. However, the possible involvement of MVs, mainly derived from smooth muscle cells, in the calcification of atherosclerotic lesions was demonstrated a long time ago [ 149 ].…”

“…EVs between them, exosomes and MVs, also have a significant role in senescence, where they are increasing more than 10-fold in most cases [ 12 , 13 , 14 ]. The pathogenesis of different diseases [ 15 ] including cardiovascular pathology [ 16 ], is a reason why they also have been used as therapeutic tools in cardiovascular disease [ 17 ]; more specifically, plasma MVs are mediators of endothelial dysfunction [ 18 ] and atherosclerosis development [ 19 , 20 , 21 , 22 ] including calcification [ 23 ].…”