Red blood cells collision with the wall in human coronary arteries promotes oxidative stress in early stage atheroma

Introduction Among the various actors involved in the coronary atherosclerosis (CAD), erythrocytes (RBC), have been little studied but they are rich in atherogenic components (cholesterol, phospholipids, Iron). RBC collision with the aortic wall has recently reported as an important source of oxidation process in early human aortic atheroma. Objective The objective was to extend these data to human coronary arteries (CAs) at different stages of CAD, with integrating hemodynamic conditions to better describe this novel mechanism and consequences on atherogenesis. Method Thirty-nine human hearts were collected with the agreement of the French Medicine Agency. Epicardial CAs were dissected and longitudinal sections were performed to integrate flow direction and shear stress vectors in histological analysis. Both iron ionic forms were studied by a co-staining with potassium ferrocyanide and H2O2/diamino-benzydine polymerization. RBC membranes were identified by glycophorin-A immuno-staining. An in vivo model of RBC collision was performed in rabbits producing an experimental carotid stenosis using a 3D printed cuff. A high resolution MRI (7 Tesla) was performed on coronary samples to better define the intra-parietal iron distribution. Iron-induced oxidative stress was evaluated in vitro by a co-culture of vascular smooth muscle cells (vSMC) with RBC. Results Among the 88 coronary samples analyzed, 72% had intraparietal iron found inside the foam cells. Redox-active Fe++ was the predominante ionic form and was observed in subendothelial level, even in healthy CAs. High resolution MRI allowed a good detection of iron in human coronaries. Multimodal analysis showed that RBC collision predominated in the post-stenotic part. RBC were phagocytosed by the vSMC inducing a cytotoxic effect on them. Conclusion Intimal RBC infiltration may be an initial trigger of foam cells formation and intraparietal oxidation in CAs. Their collision with CAs wall depends on the local hemodynamic conditions.