Abstract 164: Synthetic High-Density Lipoprotein Cholesterol Scavengers for the Treatment of Niemann-Pick C Disease

Abstract

Background: Niemann-Pick C disease (NPC) is genetic disorder caused by an accumulation of unesterified cholesterol in late endosomes and lysosomes due to defects in NPC genes. The levels of ABCA1 gene expression and concentration of high-density lipoproteins (HDL) are significantly decreased in NPC patients. Infusion of synthetic HDL (sHDL) in patients with atherosclerosis has been previously found safe (up to 100 mg/kg) and effective at reducing cholesterol in atheroma. The objective of this study is to identify sHDL composition capable of rescuing cholesterol storage in NPC. Materials and Methods: A panel of sHDL formulations was prepared by lyophilization method using commercially available Apolipoprotein A-I mimetic peptide, 5A, complexed in various ratios with phospholipids such as sphingomyelin (SM), palmitoyl-oleoyl phosphatidylcholine (POPC), or dimyristoyl phosphatidylcholine (DMPC). The efficacy of 5A alone and sHDLs was determined in primary patient NPC and wild type fibroblast cells using fluorescent filipin staining and cholesterol efflux assay. Trafficking of sHDL in NPC fibroblasts was assessed by confocal microscopy using fluorescently-labeled sHDL. Finally, in vivo study was executed to examine effects of our best sHDL formulation 5A-SM in NPC1 I1061T homozygotes and littermate controls treated with vehicle or sHDL (100 mg/kg, i.p., 3x/wk) for 4 weeks, starting at 7 wks of age. Neurological correction was accessed by the balance beam tests and body weight changes were tracked. Results: Treatment of NPC fibroblasts with sHDL resulted in a dose- and time-dependent rescue of lipid storage (5A-POPC<5A-SM<5A-DMPC). Cellular toxicity was observed only for 5A-DMPC (~30%). HDL trafficking studies revealed that sHDLs got endocytosed into cells and co-localized with LAMP1. Additionally, administration of 100 mg/kg 5A-SM resulted in a significant rescue of body weight (p<0.01) in the NPC mice with no toxicity to animals. However, neuro-correction after sHDL treatment in adult mice was not detected. The absence of neuro-correction observed in adult NPC mice suggest that the alternative delivery routes, treatment durations, or sHDL compositions are still needed.