panobinostat and Niemann-Pick-Disease--Type-C

Niemann-Pick C (NPC) disease is an autosomal recessive disorder that leads to excessive storage of cholesterol and other lipids in late endosomes and lysosomes. The large majority of NPC disease is caused by mutations in NPC1, a large polytopic membrane protein that functions in late endosomes. There are many disease-associated mutations in NPC1, and most patients are compound heterozygotes. The most common mutation, NPC1

Topics: Carrier Proteins; Cell Line; Cholesterol; Endoplasmic Reticulum-Associated Degradation; Endosomes; Fibroblasts; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Indoles; Intracellular Signaling Peptides and Proteins; Lysosomes; Membrane Glycoproteins; Mutation; Niemann-Pick C1 Protein; Niemann-Pick Disease, Type C; Panobinostat; RNA, Small Interfering; Transfection; Vorinostat

Niemann-Pick Type C disease (NPC) is a lethal, autosomal recessive disorder caused by mutations in the NPC1 and NPC2 cholesterol transport proteins. NPC's hallmark symptoms include an accumulation of unesterified cholesterol and other lipids in the late endosomal and lysosomal cellular compartments, causing progressive neurodegeneration and death. Although the age of onset may vary in those affected, NPC most often manifests in juveniles, and is usually fatal before adolescence. In this study, we investigated the effects of various drugs, many of which modify the epigenetic control of NPC1/NPC2 gene expression, in lowering the otherwise harmful elevated intracellular cholesterol levels in NPC cells. Our studies utilized a previously described image analysis technique, which allowed us to make quantitative comparisons of the efficacy of these drugs in lowering cholesterol levels in a common NPC1 mutant model. Of the drugs analyzed, several that have been previously studied (vorinostat, panobinostat, and β-cyclodextrin) significantly lowered the relative amount of unesterified cellular cholesterol, consistent with earlier observations. In addition, a novel potential treatment, rapamycin, likewise alleviated the NPC phenotype. We also studied combinations of effective compounds with β-cyclodextrin; the addition of β-cyclodextrin significantly enhanced the cholesterol-lowering activity of vorinostat and panobinostat, but had mixed effects with rapamycin. Collectively, these results may provide a basis for the eventual development of improved NPC therapies.

Topics: Azacitidine; beta-Cyclodextrins; Cells, Cultured; Child; Child, Preschool; Chloroquine; Chlorpromazine; Cholesterol; Decitabine; Dose-Response Relationship, Drug; Drug Synergism; Female; Fibroblasts; Humans; Hydroxamic Acids; Indoles; Intracellular Space; Male; Microscopy, Fluorescence; Mutation; Niemann-Pick Disease, Type C; Panobinostat; Sirolimus; Vorinostat

Niemann-Pick type C (NPC) disease is predominantly caused by mutations in the NPC1 protein that affect intracellular cholesterol trafficking and cause accumulation of unesterified cholesterol and other lipids in lysosomal storage organelles. We report the use of a series of small molecule histone deacetylase (HDAC) inhibitors in tissue culture models of NPC human fibroblasts. Some HDAC inhibitors lead to a dramatic correction in the NPC phenotype in cells with either one or two copies of the NPC1(I1061T) mutation, and for several of the inhibitors, correction is associated with increased expression of NPC1 protein. Increased NPC1(I1061T) protein levels may partially account for the correction of the phenotype, because this mutant can promote cholesterol efflux if it is delivered to late endosomes and lysosomes. The HDAC inhibitor treatment is ineffective in an NPC2 mutant human fibroblast line. Analysis of the isoform selectivity of the compounds used implicates HDAC1 and/or HDAC2 as likely targets for the observed correction, although other HDACs may also play a role. LBH589 (panobinostat) is an orally available HDAC inhibitor that crosses the blood-brain barrier and is currently in phase III clinical trials for several types of cancer. It restores cholesterol homeostasis in cultured NPC1 mutant fibroblasts to almost normal levels within 72 h when used at 40 nM. The findings that HDAC inhibitors can correct cholesterol storage defects in human NPC1 mutant cells provide the potential basis for treatment options for NPC disease.

Topics: Blotting, Western; Carrier Proteins; Cell Line; Cholesterol; Dose-Response Relationship, Drug; Fibroblasts; Gene Expression Regulation; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Image Processing, Computer-Assisted; Indoles; Intracellular Signaling Peptides and Proteins; Isoenzymes; Membrane Glycoproteins; Microscopy, Fluorescence; Mutation; Niemann-Pick C1 Protein; Niemann-Pick Disease, Type C; Panobinostat; Time Factors