Treatment of Niemann--pick type C disease by histone deacetylase inhibitors

Abstract

Niemann-Pick type C disease (NPC) is a devastating, recessive, inherited disorder that causes accumulation of cholesterol and other lipids in late endosomes and lysosomes. Mutations in 2 genes, NPC1 and NPC2, are responsible for the disease, which affects about 1 in 120,000 live births. About 95% of patients have mutations in NPC1, a large polytopic membrane protein that is normally found in late endosomes. More than 200 missense mutations in NPC1 have been found in NPC patients. The disease is progressive, typically leading to death before the age of 20 years, although some affected individuals live well into adulthood. The disease affects peripheral organs, including the liver, spleen, and lungs, but the most severe symptoms are associated with neurological disease. There are some palliative treatments that slow progression of NPC disease. Recently, it was found that histone deacetylase (HDAC) inhibitors that are effective against HDACs 1, 2, and 3 can reduce the cholesterol accumulation in fibroblasts derived from NPC patients with mutations in NPC1. One example is vorinostat. As vorinostat is a Food and Drug Administration-approved drug for treatment of cutaneous T-cell lymphoma, this opens up the possibility that HDAC inhibitors could be repurposed for treatment of this rare disease. The mechanism of action of the HDAC inhibitors requires further study, but these drugs increase the level of the NPC1 protein. This may be due to post-translational stabilization of the NPC1 protein, allowing it to be transported out of the endoplasmic reticulum.

Fig. 1

Niemann–Pick type C disease therapeutics. Miglustat (left) inhibits the synthesis of glycosphingolipids, which accumulate along with cholesterol in late endosomes and lysosomes of neurons. 2-Hydroxypropyl-β-cyclodextrin (right) binds cholesterol and solubilizes it. This can lead to efflux of stored cholesterol from late endosomes and lysosomes. NB-DNJ = n-butyldeoxygalactonojirimycin

Fig. 2

Histone deacetylase (HDAC) inhibitors previously approved by the Food and Drug Administration. The various names used for the compounds are provided. Entries in parentheses indicate the HDAC for which the strongest inhibitory effects are seen.

Fig. 3

Histone deacetylase (HDAC) inhibitors. Entries in parentheses indicate the HDAC for which the strongest inhibitory effects are seen

Fig. 4

Dose–time response for treatment of GM03123 Niemann–Pick type C disease 1 mutant cells with vorinostat. The vertical axis measures the fluorescence response of filipin staining of cholesterol in lysosomal storage organelles (LSO). Cells were treated for 48 h with varying concentrations of vorinostat. The cells were then fixed and stained with filipin

Fig. 5

Effect of vorinostat on cholesterol storage. Fluorescence microscopy images of filipin-stained GM03123 Niemann–Pick type C disease 1 mutant cells treated with dimethyl sulfoxide vehicle (a) or 10 μM vorinostat (b) for 2 days. Scale bar = 15 μm

Fig. 6

Simple, weak histone deacetylase inhibitors with therapeutic applications