J.V. Mitsios, L.D. Tsironis, A. A. Dimitriou, A. D. Tselepis
Oxidized low-density lipoprotein (oxLDL) plays an important role in atherogenesis. Platelet-derived microparticles (PMPs) are formed during platelet activation and are involved in various pathophysiological conditions including, atherosclerosis. We investigated whether PMPs could interact with LDL in vitro and in vivo and influence the LDL oxidation in vitro. PMPs were prepared from activated washed human platelets and characterized by flow cytometry. The binding of LDL to PMPs was studied by flow cytometry as well as by gradient ultracentrifugation. LDL or PMPs were oxidized by either CuSO4 or met-myoglobin. LDL binds to PMPs in a concentration-dependent manner, in vitro. Complexes of LDL with PMPs exist also in plasma and their production is enhanced during platelet activation ex vivo. PMPs at concentrations greater than 30μg/ml significantly protect LDL from oxidation a phenomenon, which is primarily attributed to their phosphatidylserine (PS) and plasmalogen content. The pathophysiological significance of these phenomena in respect to atherogenesis remains to be established.
Keywords: LDL, oxidation, platelet-derived microparticles, PMPs