Vasoprotective Functions of High-Density Lipoproteins Relevant to Alzheimer's Disease Are Partially Conserved in Apolipoprotein B-Depleted Plasma.

High-density lipoproteins (HDL) are known to have vasoprotective functions in peripheral arteries and many of these functions extend to brain-derived endothelial cells. Importantly, several novel brain-relevant HDL functions have been discovered using brain endothelial cells and in 3D bioengineered human arteries. The cerebrovascular benefits of HDL in healthy humans may partly explain epidemiological evidence suggesting a protective association of circulating HDL levels against Alzheimer's Disease (AD) risk. As several methods exist to prepare HDL from plasma, here we compared cerebrovascular functions relevant to AD using HDL isolated by density gradient ultracentrifugation relative to apoB-depleted plasma prepared by polyethylene-glycol precipitation, a common high-throughput method to evaluate HDL cholesterol efflux capacity in clinical biospecimens. We found that apoB-depleted plasma was functionally equivalent to HDL isolated by ultracentrifugation in terms of its ability to reduce vascular Aβ accumulation, suppress TNFα-induced vascular inflammation and delay Aβ fibrillization. However, only HDL isolated by ultracentrifugation was able to suppress Aβ-induced vascular inflammation, improve Aβ clearance, and induce endothelial nitric oxide production.