Effect of myeloperoxidase modified LDL on bovine and human aortic endothelial cells

Abstract

Atherosclerosis is a critical disease with multiple etiologies and causal factors; early observations have correlated fibrin deposition with atheroma plaque formation. This led to the proposition that a decrease in fibrinolysis in endothelial cells may negatively influence atherogenesis. Endothelial cells themselves maintain a stringent, dynamic and continuous equilibrium by secreting major fibrinolysis and coagulation factors. Since it has been previously confirmed that myeloperoxidase modified low density lipoprotein (MoxLDL) decreases endothelial cell profibrinolytic capacity in real-time without delineating the mechanisms by which this modified LDL can alter pericellular fibrinolysis, we tried in the present study to perform a preliminary dissection of the molecules that might be involved in decreasing fibrinolysis after MoxLDL treatment. Therefore, the initial aim of our study was to assess the effect of MoxLDL by comparing its impact on two different primary cultures of endothelial cells: bovine aortic endothelial (BAE) cells and human aortic endothelial cells (HAEC). We showed that treating BAE cells with a physiological concentration (100 μg/ml) of MoxLDL induced around 70% cell death as determined by propidium iodide staining followed by flow cytometry analysis. On the other hand, HAEC exposed to a physiological concentration of MoxLDL (100 μg/ml) maintained high viability and did not exhibit any significant variation in ROS production as measured by flow cytometry. Most importantly, qRT-PCR results did not show any effect of MoxLDL on the expression level of major fibrinolytic factors: tPA and uPA, the receptor tPAR, and the inhibitors PAI-1 and α2 macroglobulin. These data suggest that the interference of MoxLDL with pericellular fibrinolysis may be due to physical disruptions at the cell surface and not due to changes in gene expression.