Trimethylamine-N-Oxide Impedes Late Endothelial Progenitor Cell-Mediated Revascularization by Triggering Mitochondrial Apoptosis via Suppression of MnSOD

Background and Aims: Trimethylamine-N-oxide (TMAO) is recognized as a novel marker and mediator of atherosclerotic Cardiovascular Disease (ASCVD). Endothelial progenitor cells (EPCs) are crucial for maintaining vascular homeostasis. Impaired EPC numbers and function correlate with increased adverse cardiovascular events. The aim of this study was to decipher the effect of TMAO on late EPCs (LEPCs) and its underlying molecular mechanism. Methods and Results: In vitro migration and tubulogenic capacities of LEPCs were attenuated by TMAO in a dose-dependent manner, accompanied by inhibition of manganese superoxide dismutase (MnSOD) and mitochondrial damage. TMAO-induced mitochondrial damage provoked proinflammatory responses (increased levels of IL-6, IL-1b, ICAM-1, E-sel, and TNF-α) and autophagic cell death (confirmed by western blot immunofluorescent staining and transmission electron microscopy) in LEPCs. Overexpression of MnSOD through adenovirus transfection reversed TMAO-related LEPCs dysfunction. To study the effect of TMAO on LEPC-mediated vascular repair in vivo, a hind limb ischemia model was established in nude mice, and LEPCs were injected in the ischemic hind limb. Laser Doppler imaging of mouse ischemic hindlimbs at 21 days indicated that TMAO treatment inhibited LEPCs-mediated blood flow recovery, which was restored by MnSOD overexpression. Immunohistology analyses further revealed consistent alterations in capillary density determined by CD31 staining. Conclusions: TMAO induces mitochondrial damage in LEPCs via MnSOD suppression, which leads to cell dysfunction, proinflammatory activation, and autophagic cell death in vitro and impaired LEPCs-mediated revascularization in vivo. Overexpression of MnSOD restores TMAO-induced LEPCs dysfunction and further enhances LEPC-mediated revascularization in the ischemic hind limbs in nude mice.