Untargeted LC-MS/MS proteomics on supernatant of endothelial cells exposed to Myeloperoxidase-oxidized LDLs (Mox-LDLs)

Myeloperoxidase-oxidized LDLs (Mox-LDLs) trigger endothelial cells and participate in atherosclerosis. However, the mechanisms behind Mox-LDLs stimulation are not fully understood. Therefore, we used an untargeted proteomics approach to analyze human umbilical vein endothelial cells (HUVECs) after stimulation by Mox-LDLs. HUVECs (n=6) were exposed for 24 h to Mox-LDLs (0 or 100 µg/ml) with or without native LDLs (0 or 1 mg/m). Supernatant and cell lysate were then analyzed using LC-MS/MS. Mox-LDLs treatment of HUVECs led to changes in the expression of proteins implicated in hemostasis, cell adhesion, angiogenesis, inflammation and stress responses. We also observed cell reprogramming through increased mitochondrial activity. Mox-LDLs seem to induce mitochondrial activation and oxidative stress in the cell, likely reactive oxygen species mediated. We suggest that HUVECs then activate cytoprotective antioxidant coping mechanisms (glutathione synthesis, heme oxygenase-1) to survive. Mox-LDLs may also modulate hemostasis and inflammatory responses, both pro- and anti-inflammatory.