Abstract 434: LDL Apheresis Significantly Alters HDL Cargo and Function in Familial Hypercholesterolemia Subjects

Abstract

In addition to cholesterol, HDL transports a wide-variety of cargo including vitamins, nucleic acids, and a diverse set of proteins. Outside of the reverse cholesterol transport pathway, HDL has alternative functions that contribute to its anti-atherogenicity, including anti-inflammatory, anti-oxidant, and signaling capacities. Recently, we found that HDL transports and delivers functional microRNAs to recipient cells, which likely confers HDL’s ability to suppress adhesion molecule expression in endothelial cells. As such, changes to HDL’s cargo impact many of these alternative functions, and thus its protective capacity. HDL dysfunction has been identified among patients with familial hypercholesterolemia (FH), an inherited disease due to mutations in the LDL receptor and associated with severe elevations in LDL-cholesterol (LDL-C) levels, which may necessitate LDL apheresis (LA) in management. Here we demonstrate that LA significantly alters HDL’s miRNA and protein signatures. We believe that these changes may have profound consequences on HDL’s protective capacity. Using density-gradient ultracentrifugation, we found 31 proteins to be significantly altered on HDL after LA, as determined by shotgun proteomics and multidimensional protein identification technology analysis. For example, vitamin D-binding protein (1.74-fold) was increased, while lipopolysaccharide-binding protein (-1.92-fold), platelet-activating factor acetylhydrolase (-2.06), and apolipoprotein A-V (-2.4-fold) were found to be decreased. Gene ontology and KEGG enrichment analysis demonstrated roles of these proteins in response to stress, coagulation, hemostasis, and vesicle-mediated transport. Fast-protein liquid chromatography was used to further purify HDL for miRNA profiling using TaqMan OpenArrays, and we found 8 HDL-miRNAs to be significantly altered -- 3 down (miR-302b -13.9-fold, miR-224 -1.8, miR-572 -2.4-fold) and 5 up (miR-7 9.8-fold, miR-208b 16.2-fold, miR-34a-3p 3-fold, miR-627 2.4-fold, miR-1183 4.8-fold). Both miR-302b and miR-224 decreased; these are miRNAs previously reported to suppress proliferation through targeting AKT2 and apoptosis, respectively. As such, these changes likely alter HDL’s function in FH subjects.