Synthetic Lipid Scavengers for the Treatment of Niemann‐Pick C Disease
Authors: Fawaz Maria V. , Schultz Mark L. , Liu Elaine , Ming Ran , Morin Emily E. , Lieberman Andrew P. , Schwendeman Anna 
Published: June 2021

BackgroundNiemann‐Pick C disease(NPC) is genetic disorder caused by an accumulation of unesterified cholesterolin late endosomes and lysosomes due to defects in NPC1 (95%) and NPC2(5%). Symptoms commonly start inperipheral organs, then progress to severe neurological dysfunction and death with the life expectancy depending on the disease severity. Cyclodextrin was found to be effective in scavenging cellular cholesterol and improving neurological symptoms, but it required frequent intrathecal administrations and led to severe hearing loss. Infusion of synthetic HDL (sHDL) in patients with atherosclerosis has been previously found safe (upto 100 mg/kg) and effective at reducing cholesterol accumulations in arterial plaques. The objective of this research is to identify sHDL composition capable of rescuing cholesterol storage in NPC without toxicity.Materials and MethodsA panel of sHDL formulations was prepared by lyophilization method using 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 size and morphology of resulting sHDLs were characterized by dynamic light scattering and transmission electron miscopy. The ability of 5A peptide and sHDLs (0.031,0.325, 0.750 mg/mL) to scavenge an excess of cholesterol from NPC patient primary fibroblast cells was determined using fluorescent filip in staining and [3H]cholesterol efflux assay. Trafficking of sHDL was assessed by incubating NPC cells with fluorescently‐labeled (DiA or DiD, AlexaFluor647) particles and lysosomal marker LAMP1 followed by visualization under confocal microscope. 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 detected by the balance beam test.ResultsProduced sHDL particles had homogeneous size distribution (~10 nm) and characteristic discoidal shape. Treatment with sHDL resulted in a dose‐, time‐, and sHDL composition‐dependent rescue of cholesterol storage in NPC fibroblasts (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 correction of peripheral NPC disease as noted by a rescue of body weight (p<0.01) with no toxicity to animals. However, no neuro correction after sHDL treatment in adult mice was detected.ConclusionsHDL, particularly 5A‐SM, was found to be effective at rescuing cholesterol accumulations in NPC cells and resulted in robust correction of bodyweight loss in NPC mice. The absence of neuro correction observed in adult NPC mice suggest that the alternative delivery routes, treatment durations, or sHDL composition optimization are still needed.Support or Funding InformationNIH T32‐GM007767, Ara Parseghian Medical Research Foundation, University of Michigan Protein Folding Diseases InitiativeThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.