Abstract 16549: Trimethylamine N-Oxide-Derived Endothelial Microvesicles Induce a Dysfunctional Endothelial Cell Phenotype

Abstract

Introduction: Gut microbiota-generated increases in trimethylamine N-oxide (TMAO) has been linked to atherosclerosis and major adverse cardiovascular events. Experimental and clinical studies suggest that TMAO impairs endothelial cell function resulting in a proatherogenic endothelial phenotype. Endothelial microvesicles (EMVs) are anucleate vesicles shed constitutively by the endothelium aiding in cell-to-cell communication, activate repair or defense mechanisms, and/or stimulate immune responses. Under pathologic conditions, however, EMVs are released in greater number and their functional phenotype is more likely to evoke dysfunctional cellular effects. The experimental aims of this study were to determine: 1) if TMAO stimulates EMV release from endothelial cells in vitro ; and 2) the effects of TMAO-generated EMVs on endothelial cell inflammation, apoptosis, autophagy and nitric oxide (NO) production. Methods: Human umbilical vein endothelial cells (HUVECs) were treated with TMAO (100 μmol) for 24 h. EMVs released into the supernatant from cells treated with TMAO or vehicle were isolated and quantified by flow cytometry. Fresh HUVECs were treated with either TMAO-derived or control EMVs for 24 h. Results: EMV release was significantly higher in cells treated with TMAO compared with control (55±3 vs 28±3 EMV/μL). TMAO-generated EMVs induced significantly higher release of interleukin (IL)-6 (33.9±2.6 vs 20.2±1.3 pg/mL) and IL-8 (45.4±2.6 vs 33.1±1.6 pg/mL) and active NF-κB p65 (Ser536) (17.4±1.3 vs 7.7±1.0 AU) expression than control EMVs. TMAO EMVs significantly increased cell expression of apoptotic proteins caspase-9 (198.5±19.4 vs 119.7±11.2 AU) and active caspase-3 (17.7±2.8 vs 11.3±0.7 AU) and markedly depressed eNOS activity (10.6±0.9 vs 6.9±0.6 AU) and NO production (7.7±0.4 vs 5.5±0.6 μmol/L). In addition, cell autophagy was dysregulated by TMAO EMVs; cell expression of Beclin-1 (53.8±6.4 vs 36.6±3.6 AU), p62 (34.0±0.8 vs 16.9±1.2 AU) and LC3BII/LC3BI (15.0±0.1 vs 7.5±0.8 AU) were significantly elevated in cells treated with TMAO vs control EMVs. Conclusions: TMAO-generated EMVs adversely affect major functional characteristics of endothelial cells potentially contributing to the proatherogenic profile of TMAO.