Impaired high-density lipoprotein anti-oxidant capacity in human abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a particular form of atherothrombotic disease characterized by the dilation of the aortic wall and the presence of an intraluminal thrombus (ILT). The objective of the present study was to evaluate the pro-oxidant properties of the ILT and to characterize the anti-oxidant capacity of high-density lipoproteins (HDLs). Our results show that ILT, adventitia, and plasma from AAA patients contained high concentrations of lipid and protein oxidation products. Mediators produced within or released by the thrombus and the adventitia were shown to induce reactive oxygen species (ROS) production by cultured aortic smooth muscle cells (AoSMCs) and to trigger the onset of apoptosis (an increase in mitochondrial membrane potential). Iron chelation limited these effects. Both concentration and functionality of HDLs were altered in AAA patients. Plasma levels of Apo A-I were lower, and small HDL subclasses were decreased in AAA patients. Circulating HDLs in AAA patients displayed an impaired capacity to inhibit copper-induced low-density lipoprotein oxidation and AoSMC ROS production. Western blot analyses of HDLs demonstrated that myeloperoxidase is associated with HDL particles in AAA patients. ILT and adventitia are a source of pro-oxidant products, in particular haemoglobin, which may impact on the wall stability/rupture in AAA. In addition, HDLs from AAA patients exhibit an impaired anti-oxidant activity. In this context, restoring HDL functionality may represent a new therapeutic option in AAA.