Microglia activation in Niemann-Pick disease, type C1 is amendable to therapeutic intervention.

Niemann-Pick disease, type C1 (NPC1) is a neurodegenerative disorder with limited treatment options. NPC1 is associated with neuroinflammation; however, attempts to therapeutically target neuroinflammation in NPC1 have had mixed success. We show here that NPC1 neuroinflammation is characterized by an atypical microglia activation phenotype. Specifically, Npc1-/- microglia demonstrated altered morphology, reduced levels of lineage markers and a shift toward glycolytic metabolism. Treatment with 2-hydroxypropyl-ß-cyclodextrin (HPßCD), a drug currently being studied in a phase 2b/3 clinical trial, reversed all microglia-associated defects in Npc1-/- animals. In addition, impairing microglia mediated neuroinflammation by genetic deletion of IRF8 led to decreased symptoms and increased lifespan. We identified CD22 as a marker of dysregulated microglia in Npc1 mutant mice and subsequently demonstrated that elevated cerebrospinal fluid levels of CD22 in NPC1 patients responds to HPßCD administration. Collectively, these data provide the first in-depth analysis of microglia function in NPC1 and suggest possible new therapeutic approaches.

Gastrointestinal Tract Pathology in a BALB/c Niemann-Pick Disease Type C1 Null Mouse Model.

BACKGROUND: Niemann-Pick disease, type C (NPC) is a rare lysosomal storage disorder characterized by progressive neurodegeneration, splenomegaly, hepatomegaly, and early death. NPC is caused by mutations in either the NPC1 or NPC2 gene. Impaired NPC function leads to defective intracellular transport of unesterified cholesterol and its accumulation in late endosomes and lysosomes. A high frequency of Crohn disease has been reported in NPC1 patients, suggesting that gastrointestinal tract pathology may become a more prominent clinical issue if effective therapies are developed to slow the neurodegeneration. The Npc1 nih mouse model on a BALB/c background replicates the hepatic and neurological disease observed in NPC1 patients. Thus, we sought to characterize the gastrointestinal tract pathology in this model to determine whether it can serve as a model of Crohn disease in NPC1. METHODS: We analyzed the gastrointestinal tract and isolated macrophages of BALB/cJ cNctr-Npc1m1N/J (Npc1-/-) mouse model to determine whether there was any Crohn-like pathology or inflammatory cell activation. We also evaluated temporal changes in the microbiota by 16S rRNA sequencing of fecal samples to determine whether there were changes consistent with Crohn disease. RESULTS: Relative to controls, Npc1 mutant mice demonstrate increased inflammation and crypt abscesses in the gastrointestinal tract; however, the observed pathological changes are significantly less than those observed in other Crohn disease mouse models. Analysis of Npc1 mutant macrophages demonstrated an increased response to lipopolysaccharides and delayed bactericidal activity; both of which are pathological features of Crohn disease. Analysis of the bacterial microbiota does not mimic what is reported in Crohn disease in either human or mouse models. We did observe significant increases in cyanobacteria and epsilon-proteobacteria. The increase in epsilon-proteobacteria may be related to altered cholesterol homeostasis since cholesterol is known to promote growth of this bacterial subgroup. CONCLUSIONS: Macrophage dysfunction in the BALB/c Npc1-/- mouse is similar to that observed in other Crohn disease models. However, neither the degree of pathology nor the microbiota changes are typical of Crohn disease. Thus, this mouse model is not a good model system for Crohn disease pathology reported in NPC1 patients.