Niemann-Pick disease type C. Study on the nature of the cerebral storage process

Differently increased volumes of multiple brain areas in Npc1 mutant mice following various drug treatments

Background

Niemann-Pick disease type C1 (NPC1, MIM 257220) is a heritable lysosomal storage disease characterized by a progressive neurological degeneration that causes disability and premature death. A murine model of Npc1-/- displays a rapidly progressing form of Npc1 disease, which is characterized by weight loss, ataxia, and increased cholesterol storage. Npc1-/- mice receiving a combined therapy (COMBI) of miglustat (MIGLU), the neurosteroid allopregnanolone (ALLO) and the cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (HPßCD) showed prevention of Purkinje cell loss, improved motor function and reduced intracellular lipid storage. Although therapy of Npc1-/- mice with COMBI, MIGLU or HPßCD resulted in the prevention of body weight loss, reduced total brain weight was not positively influenced.

Methods

In order to evaluate alterations of different brain areas caused by pharmacotherapy, fresh volumes (volumes calculated from the volumes determined from paraffin embedded brain slices) of various brain structures in sham- and drug-treated wild type and mutant mice were measured using stereological methods.

Results

In the wild type mice, the volumes of investigated brain areas were not significantly altered by either therapy. Compared with the respective wild types, fresh volumes of specific brain areas, which were significantly reduced in sham-treated Npc1-/- mice, partly increased after the pharmacotherapies in all treatment strategies; most pronounced differences were found in the CA1 area of the hippocampus and in olfactory structures.

Discussion

Volumes of brain areas of Npc1-/- mice were not specifically changed in terms of functionality after administering COMBI, MIGLU, or HPßCD. Measurements of fresh volumes of brain areas in Npc1-/- mice could monitor region-specific changes and response to drug treatment that correlated, in part, with behavioral improvements in this mouse model.

The Npc2Gt(LST105)BygNya mouse signifies pathological changes comparable to human Niemann-Pick type C2 disease

INTRODUCTION

Niemann-Pick type C2 disease (NP-C2) is a fatal neurovisceral disorder caused by defects in the lysosomal cholesterol transporter protein NPC2. Consequently, cholesterol and other lipids accumulate within the lysosomes, causing a heterogeneous spectrum of clinical manifestations. Murine models are essential for increasing the understanding of the complex pathology of NP-C2. This study, therefore, aims to describe the neurovisceral pathology in the NPC2-deficient mouse model to evaluate its correlation to human NP-C2.

METHODS

Npc2-/- mice holding the LST105 mutation were used in the present study (Npc2Gt(LST105)BygNya). Body and organ weight and histopathological evaluations were carried out in six and 12-week-old Npc2-/- mice, with a special emphasis on neuropathology. The Purkinje cell (PC) marker calbindin, the astrocytic marker GFAP, and the microglia marker IBA1 were included to assess PC degeneration and neuroinflammation, respectively. In addition, the pathology of the liver, lungs, and spleen was assessed using hematoxylin and eosin staining.

RESULTS

Six weeks old pre-symptomatic Npc2-/- mice showed splenomegaly and obvious neuropathological changes, especially in the cerebellum, where initial PC loss and neuroinflammation were evident. The Npc2-/- mice developed neurological symptoms at eight weeks of age, severely progressing until the end-stage of the disease at 12 weeks. At the end-stage of the disease, Npc2-/- mice were characterized by growth retardation, tremor, cerebellar ataxia, splenomegaly, foam cell accumulation in the lungs, liver, and spleen, brain atrophy, pronounced PC degeneration, and severe neuroinflammation.

CONCLUSION

The Npc2Gt(LST105)BygNya mouse model resembles the pathology seen in NP-C2 patients and denotes a valuable model for increasing the understanding of the complex disease manifestation and is relevant for testing the efficacies of new treatment strategies.

Identification of Brain-Specific Treatment Effects in NPC1 Disease by Focusing on Cellular and Molecular Changes of Sphingosine-1-Phosphate Metabolism

Niemann-Pick type C1 (NPC1) is a lysosomal storage disorder, inherited as an autosomal-recessive trait. Mutations in the Npc1 gene result in malfunction of the NPC1 protein, leading to an accumulation of unesterified cholesterol and glycosphingolipids. Beside visceral symptoms like hepatosplenomegaly, severe neurological symptoms such as ataxia occur. Here, we analyzed the sphingosine-1-phosphate (S1P)/S1P receptor (S1PR) axis in different brain regions of Npc1^-/- mice and evaluated specific effects of treatment with 2-hydroxypropyl-β-cyclodextrin (HPβCD) together with the iminosugar miglustat. Using high-performance thin-layer chromatography (HPTLC), mass spectrometry, quantitative real-time PCR (qRT-PCR) and western blot analyses, we studied lipid metabolism in an NPC1 mouse model and human skin fibroblasts. Lipid analyses showed disrupted S1P metabolism in Npc1^-/- mice in all brain regions, together with distinct changes in S1pr3/S1PR3 and S1pr5/S1PR5 expression. Brains of Npc1^-/- mice showed only weak treatment effects. However, side effects of the treatment were observed in Npc1^+/+ mice. The S1P/S1PR axis seems to be involved in NPC1 pathology, showing only weak treatment effects in mouse brain. S1pr expression appears to be affected in human fibroblasts, induced pluripotent stem cells (iPSCs)-derived neural progenitor and neuronal differentiated cells. Nevertheless, treatment-induced side effects make examination of further treatment strategies indispensable.

Current Challenges in Understanding the Cellular and Molecular Mechanisms in Niemann-Pick Disease Type C1

Rare diseases are a heterogeneous group of very different clinical syndromes. Their most common causes are defects in the hereditary material, and they can therefore be passed on to descendants. Rare diseases become manifest in almost all organs and often have a systemic expressivity, i.e., they affect several organs simultaneously. An effective causal therapy is often not available and can only be developed when the underlying causes of the disease are understood. In this review, we focus on Niemann–Pick disease type C1 (NPC1), which is a rare lipid-storage disorder. Lipids, in particular phospholipids, are a major component of the cell membrane and play important roles in cellular functions, such as extracellular receptor signaling, intracellular second messengers and cellular pressure regulation. An excessive storage of fats, as seen in NPC1, can cause permanent damage to cells and tissues in the brain and peripheral nervous system, but also in other parts of the body. Here, we summarize the impact of NPC1 pathology on several organ systems, as revealed in experimental animal models and humans, and give an overview of current available treatment options.

Insights into the Molecular Mechanisms of Cholesterol Binding to the NPC1 and NPC2 Proteins

In recent years, a growing number of studies have implicated the coordinated action of NPC1 and NPC2 in intralysosomal transport and efflux of cholesterol. Our current understanding of this process developed with just over two decades of research. Since the cloning of the genes encoding the NPC1 and NPC2 proteins, studies of the biochemical defects observed when either gene is mutated along with computational and structural studies have unraveled key steps in the underlying mechanism. Here, we summarize the major contributions to our understanding of the proposed cholesterol transport controlled by NPC1 and NPC2, and briefly discuss recent findings of cholesterol binding and transport proteins beyond NPC1 and NPC2. We conclude with key questions and major challenges for future research on cholesterol transport by the NPC1 and NPC2 proteins.

Olfactory Performance as an Indicator for Protective Treatment Effects in an Animal Model of Neurodegeneration

Background: Neurodegenerative diseases are often accompanied by olfactory deficits. Here we use a rare neurovisceral lipid storage disorder, Niemann–Pick disease C1 (NPC1), to illustrate disease-specific dynamics of olfactory dysfunction and its reaction upon therapy. Previous findings in a transgenic mouse model (NPC1^-/-) showed severe morphological and electrophysiological alterations of the olfactory epithelium (OE) and the olfactory bulb (OB) that ameliorated under therapy with combined 2-hydroxypropyl-ß-cyclodextrin (HPßCD)/allopregnanolone/miglustat or HPßCD alone.

Methods: A buried pellet test was conducted to assess olfactory performance. qPCR for olfactory key markers and several olfactory receptors was applied to determine if their expression was changed under treatment conditions. In order to investigate the cell dynamics of the OB, we determined proliferative and apoptotic activities using a bromodeoxyuridine (BrdU) protocol and caspase-3 (cas-3) activity. Further, we performed immunohistochemistry and western blotting for microglia (Iba1), astroglia (GFAP) and tyrosine hydroxylase (TH).

Results: The buried pellet test revealed a significant olfactory deterioration in NPC1^-/- mice, which reverted to normal levels after treatment. At the OE level, mRNA for olfactory markers showed no changes; the mRNA level of classical olfactory receptor (ORs) was unaltered, that of unique ORs was reduced. In the OB of untreated NPC1^-/- mice, BrdU and cas-3 data showed increased proliferation and apoptotic activity, respectively. At the protein level, Iba1 and GFAP in the OB indicated increased microgliosis and astrogliosis, which was prevented by treatment.

Conclusion: Due to the unique plasticity especially of peripheral olfactory components the results show a successful treatment in NPC1 condition with respect to normalization of olfaction. Unchanged mRNA levels for olfactory marker protein and distinct olfactory receptors indicate no effects in the OE in NPC1^-/- mice. Olfactory deficits are thus likely due to central deficits at the level of the OB. Further studies are needed to examine if olfactory performance can also be changed at a later onset and interrupted treatment of the disease. Taken together, our results demonstrate that olfactory testing in patients with NPC1 may be successfully used as a biomarker during the monitoring of the treatment.

Impact of the Niemann-Pick c1 Gene Mutation on the Total Cellular Glycomics of CHO Cells

Niemann-Pick disease type C (NPC) is an autosomal recessive lipid storage disorder, and the majority of cases are caused by mutations in the NPC1 gene. In this study, we clarified how a single gene mutation in the NPC1 gene impacts the cellular glycome by analyzing the total glycomic expression profile of Chinese hamster ovary cell mutants defective in the Npc1 gene (Npc1 KO CHO cells). A number of glycomic alterations were identified, including increased expression of lactosylceramide, GM1, GM2, GD1, various neolacto-series glycosphingolipids, and sialyl-T (O-glycan), which was found to be the major sialylated protein-bound glycan, as well as various N-glycans, which were commonly both fucosylated and sialylated. We also observed significant increases in the total amounts of free oligosaccharides (fOSs), especially in the unique complex- and hybrid-type fOSs. Treatment of Npc1 KO CHO cells with 2-hydroxypropyl-β-cyclodextrin (HPBCD), which can reduce cholesterol and glycosphingolipid (GSL) storage, did not affect the glycomic alterations observed in the GSL-, N-, and O-glycans of Npc1 KO CHO cells. However, HPBCD treatment corrected the glycomic alterations observed in fOSs to levels observed in wild-type cells.

Cognition and anatomy of adult Niemann-Pick disease type C: Insights for the Alzheimer field

Niemann-Pick disease type C (NPC) is a rare lysosomal storage disorder causing an intracellular lipid trafficking defect and varying damage to the spleen, liver, and central nervous system. The adult form, representing approximately 20% of the cases, is associated with progressive cognitive decline. Intriguingly, brains of adult NPC patients exhibit neurofibrillary tangles, a characteristic hallmark of Alzheimer's disease (AD). However, the cognitive, psychiatric, and neuropathological features of adult NPC and their relation to AD have yet to be explored. We systematically reviewed the literature on adult NPC with a particular focus on cognitive and neuroanatomical abnormalities. The careful study of cognition in adult NPC allows drawing critical insights in our understanding of the pathophysiology of AD as well as normal cognition.

Increased Regenerative Capacity of the Olfactory Epithelium in Niemann-Pick Disease Type C1

Niemann–Pick disease type C1 (NPC1) is a fatal neurovisceral lysosomal lipid storage disorder. The mutation of the NPC1 protein affects the homeostasis and transport of cholesterol and glycosphingolipids from late endosomes/lysosomes to the endoplasmic reticulum resulting in progressive neurodegeneration. Since olfactory impairment is one of the earliest symptoms in many neurodegenerative disorders, we focused on alterations of the olfactory epithelium in an NPC1 mouse model. Previous findings revealed severe morphological and immunohistochemical alterations in the olfactory system of NPC1^−/− mutant mice compared with healthy controls (NPC1^+/+). Based on immunohistochemical evaluation of the olfactory epithelium, we analyzed the impact of neurodegeneration in the olfactory epithelium of NPC1^−/− mice and observed considerable loss of mature olfactory receptor neurons as well as an increased number of proliferating and apoptotic cells. Additionally, after administration of two different therapy approaches using either a combination of miglustat, 2-hydroxypropyl-β-cyclodextrin (HPβCD) and allopregnanolone or a monotherapy with HPβCD, we recorded a remarkable reduction of morphological damages in NPC1^−/− mice and an up to four-fold increase of proliferating cells within the olfactory epithelium. Numbers of mature olfactory receptor neurons doubled after both therapy approaches. Interestingly, we also observed therapy-induced alterations in treated NPC1^+/+ controls. Thus, olfactory testing may provide useful information to monitor pharmacologic treatment approaches in human NPC1.

Reduced Myelin Water in the White Matter Tracts of Patients with Niemann-Pick Disease Type C

Previous studies using diffusion tensor imaging to examine white matter in Niemann-Pick disease type C have produced mixed results. However, diffusion tensor imaging does not directly measure myelin and may be affected by other structural changes. We used myelin water imaging to more directly examine demyelination in 2 patients with Niemann-Pick disease type C. The results suggest that this technique may be useful for identifying regional changes in myelination in this condition.

Intracisternal cyclodextrin prevents cerebellar dysfunction and Purkinje cell death in feline Niemann-Pick type C1 disease

Niemann-Pick type C1 (NPC) disease is a lysosomal storage disease caused by mutations in the NPC1 gene, leading to an increase in unesterified cholesterol and several sphingolipids, and resulting in hepatic disease and progressive neurological disease. We show that subcutaneous administration of the pharmaceutical excipient 2-hydroxypropyl-β-cyclodextrin (HPβCD) to cats with NPC disease ameliorated hepatic disease, but doses sufficient to reduce neurological disease resulted in pulmonary toxicity. However, direct administration of HPβCD into the cisterna magna of presymptomatic cats with NPC disease prevented the onset of cerebellar dysfunction for greater than a year and resulted in a reduction in Purkinje cell loss and near-normal concentrations of cholesterol and sphingolipids. Moreover, administration of intracisternal HPβCD to NPC cats with ongoing cerebellar dysfunction slowed disease progression, increased survival time, and decreased the accumulation of brain gangliosides. An increase in hearing threshold was identified as a potential adverse effect. These studies in a feline animal model have provided critical data on efficacy and safety of drug administration directly into the central nervous system that will be important for advancing HPβCD into clinical trials.

Observational, retrospective study of a large cohort of patients with Niemann-Pick disease type C in the Czech Republic: a surprisingly stable diagnostic rate spanning almost 40 years

Background

Niemann-Pick disease type C (NPC) is a rare, fatal neurovisceral disorder with autosomal recessive inheritance, and featuring striking clinical variability dependent on the age at onset of neurological symptoms. We report data from a large cohort of 56 Czech patients with NPC diagnosed over a period of 37 years.

Methods

An observational, retrospective analysis of historic and current clinical and laboratory information was performed among all NPC patients originating from the area of the contemporary Czech Republic and diagnosed between 1975 and 2012. All patients with ≥1 positive diagnostic test and relevant clinical information were included. Data on diagnostic methods (histopathological and/or ultrastructural; biochemical; genetic), clinical status and general information on treatment were collated. Data were examined in accordance with international guidelines for the management of NPC.

Results

Between 1975 and 1985 diagnoses were based exclusively on specific histopathological findings, often at autopsy. Bone marrow smear (BMS) analyses have proved to be a very specific indicator for NPC and have become an important part of our diagnostic algorithm. Filipin staining and cholesterol esterification assays became the definitive diagnostic tests after 1985 and were applied in 24 of our patients. Since 2005, more and more patients have been assessed using NPC1/NPC2 gene sequencing. Twelve patients were diagnosed with neonatal/early-infantile onset NPC, 13 with the late-infantile onset form, 20 with the juvenile onset form, and nine with the adolescent/adult onset form. Two diagnosed patients remained neurologically asymptomatic at study completion. Nineteen patients were siblings. Causal NPC1 mutations were determined in 38 patients; two identical NPC2 mutations were identified in one patient. In total, 30 different mutations were identified, 14 of which have been confirmed as novel. The frequency of individual mutated NPC1 alleles in our cohort differs compared with previous published data: the most frequent mutant NPC1 allele was p.R1186H (n = 13), followed by p.P1007A (n = 8), p.S954L (n = 8) and p.I1061T (n = 4).

Conclusions

These data demonstrate the evolution of the diagnostic process in NPC over the last four decades. We estimate the contemporary birth prevalence of NPC in the Czech Republic at 0.93 per 100,000.

Neuronopathic lysosomal storage diseases: clinical and pathologic findings

BACKGROUND

The lysosomal-autophagocytic system diseases (LASDs) affect multiple body systems including the central nervous system (CNS). The progressive CNS pathology has its onset at different ages, leading to neurodegeneration and early death.

METHODS

Literature review provided insight into the current clinical neurological findings, phenotypic spectrum, and pathogenic mechanisms of LASDs with primary neurological involvement.

CONCLUSIONS

CNS signs and symptoms are variable and related to the disease-specific underlying pathogenesis. LAS dysfunction leads to diverse global cellular consequences in the CNS ranging from specific axonal and dendritic abnormalities to neuronal death. Pathogenic mechanisms for disease progression vary from impaired autophagy, massive storage, regional involvement, to end-stage inflammation. Some of these features are also found in adult neurodegenerative disorders, for example, Parkinson's and Alzheimer's diseases. Lack of effective therapies is a significant unmet medical need.

The autophagic defect in Niemann-Pick disease type C neurons differs from somatic cells and reduces neuronal viability

Niemann-Pick disease type C (NPC) is a fatal, progressive neurovisceral disorder. Several studies report that the autophagic flux is disturbed in NPC1-deficient (NPC1-/-) cells. Since it has been suggested that the autophagic defect may contribute to the neurodegeneration, we used cell cultures of NPC1-deficient and NPC1-wildtype neurons to investigate whether the disturbance influences neuronal survival. We found a genotype-dependent difference in survival, when autophagy is induced during culturing. NPC1-deficient neurons are more sensitive to rapamycin treatment and starvation than wildtype neurons. The subsequent search for defects in regulatory components of the autophagic pathway and the autophagic flux brought up results which differ from previous reports on somatic cells in one essential aspect: we exclude that an enhanced formation of autophagosomes contributes to the imbalanced autophagic flux in NPC1 deficient neurons. We found that solely the clearance of autophagosomes is delayed in these cells, which leads to an accumulation of autophagic vacuoles within the lysosomal compartment. Lowering the abnormal lipid load of the acidic organelles with cyclodextrin is sufficient to correct the autophagic flux and prevents premature death of NPC1-/- neurons under autophagic stress. From our results, we conclude that a pharmacological intervention in the neuropathology of NPC-disease should focus on the restoration of the lysosomal degradation capacity of cells.

The neuropsychiatry of inborn errors of metabolism

A number of metabolic disorders that affect the central nervous system can present in childhood, adolescence or adulthood as a phenocopy of a major psychiatric syndrome such as psychosis, depression, anxiety or mania. An understanding and awareness of secondary syndromes in metabolic disorders is of great importance as it can lead to the early diagnosis of such disorders. Many of these metabolic disorders are progressive and may have illness-modifying treatments available. Earlier diagnosis may prevent or delay damage to the central nervous system and allow for the institution of appropriate treatment and family and genetic counselling. Metabolic disorders appear to result in neuropsychiatric illness either through disruption of late neurodevelopmental processes (metachromatic leukodystrophy, adrenoleukodystrophy, GM2 gangliosidosis, Niemann-Pick type C, cerebrotendinous xanthomatosis, neuronal ceroid lipofuscinosis, and alpha mannosidosis) or via chronic or acute disruption of excitatory/inhibitory or monoaminergic neurotransmitter systems (acute intermittent porphyria, maple syrup urine disease, urea cycle disorders, phenylketonuria and disorders of homocysteine metabolism). In this manuscript we review the evidence for neuropsychiatric illness in major metabolic disorders and discuss the possible models for how these disorders result in psychiatric symptoms. Treatment considerations are discussed, including treatment resistance, the increased propensity for side-effects and the possibility of some treatments worsening the underlying disorder.

Niemann-Pick disease type C1 predominantly involving the frontotemporal region, with cortical and brainstem Lewy bodies: an autopsy case

Niemann-Pick disease type C (NPC) is an autosomal recessive neurovisceral lipid storage disorder. Two disease-causing genes (NPC1 and NPC2) have been identified. NPC is characterized by neuronal and glial lipid storage and NFTs. Here, we report a man with juvenile-onset progressive neurological deficits, including pyramidal signs, ataxia, bulbar palsy, vertical supranuclear ophthalmoplegia, and psychiatric symptoms; death occurred at age 37 before definitive clinical diagnosis. Post mortem gross examination revealed a unique distribution of brain atrophy, predominantly in the frontal and temporal lobes. Microscopically, lipid storage in neurons and widely distributed NFTs were observed. Lipid storage cells appeared in systemic organs and filipin staining indicated intracellular cholesterol accumulation in hepatic macrophages. Electron microscopy revealed accumulation of lipids and characteristic oligolamellar inclusions. These findings suggested an NPC diagnosis. Neuronal loss and gliosis were frequently accompanied by NFTs and occurred in the frontal and temporal cortices, hippocampus, amygdala, basal forebrain, basal ganglia, thalamus, substantia nigra and brain stem nuclei. Lewy bodies (LBs) were observed in most, but not all, regions where NFTs were evident. In contrast, neuronal lipid storage occurred in more widespread areas, including the parietal and occipital cortices where neurodegeneration with either NFTs or LBs was minimal. Molecular genetic analysis demonstrated that the patient had compound heterozygous mutations in the cysteine-rich loop (A1017T and Y1088C) of the NPC1 gene. To our knowledge there has been no previous report of the A1017T mutation. The pathological features of this patient support the notion that NPC has an aspect of α-synucleinopathy, and long-term survivors of NPC may develop a frontotemporal-predominant distribution of brain atrophy.

Electrodiagnostic testing and histopathologic changes confirm peripheral nervous system myelin abnormalities in the feline model of niemann-pick disease type C

Niemann-Pick disease type C (NPC disease) is an incurable, neurodegenerative, autosomal recessive disease caused by mutations in either the NPC1 or the NPC2 gene. These mutations affect the intracellular trafficking of lipids and cholesterol, resulting in the intralysosomal accumulation of unesterified cholesterol and glycosphingolipids. These abnormalities are associated with clinical ataxia and impaired motor and intellectual development, and death frequently occurs in adolescence. The incidence of peripheral neuropathy in NPC patients is not known. We investigated peripheral nerves in the naturally occurring feline model of NPC disease, which has proven to be critical for understanding both disease pathogenesis and for evaluating experimental therapies. Electrodiagnostic studies revealed significantly slowed motor and sensory nerve conduction velocities in affected cats in the absence of altered M-wave amplitude. Histologic and ultrastructural analyses showed thin myelin sheaths, membranous debris, myelin figures, lipid vacuolization of Schwann cell cytoplasm, and expanded paranodal areas. Axonal degeneration was not identified. There was a shift to small myelinated fibers in affected cats, and there were significant decreases in fiber diameter, axon diameter, and myelin thickness. These changes were similar to those described in the murine NPC disease model and in rare patients in whom nerve biopsy has been performed. Characterization of the demyelinating neuropathy is necessary for evaluating clinical trials that target only the CNS aspects of NPC.

A human neuronal model of Niemann Pick C disease developed from stem cells isolated from patient's skin

Background

Niemann Pick C (NPC) disease is a neurovisceral lysosomal storage disorder due to mutations in NPC1 or NPC2 genes, characterized by the accumulation of endocytosed unesterified cholesterol, gangliosides and other lipids within the lysosomes/late endosomes. Even if the neurodegeneration is the main feature of the disease, the analysis of the molecular pathways linking the lipid accumulation and cellular damage in the brain has been challenging due to the limited availability of human neuronal models.

Objective

The aim of this study was to develop a human neuronal model of NPC disease by inducing neuronal differentiation of multipotent adult stem cells (MASC) isolated from NPC patients.

Methods

Stem cells were isolated from 3 NPC patients and 3 controls both from skin biopsies and previously established skin fibroblast cultures. Cells were induced to differentiate along a neuronal fate adapting methods previously described by Beltrami et al, 2007. The surface immunophenotype of stem cells was analyzed by FACS. Stem cell and neuronal markers expression were evaluated by immunofluorescence. Intracellular accumulation of cholesterol and gangliosides were assessed by filipin staining and immunofluorescence, respectively. A morphometric analysis was performed using a Neurite outgrowth image program.

Results

After 3 passages in selective medium, MASC isolated either from skin biopsies or previously established skin fibroblast cultures displayed an antigenic pattern characteristic of mesenchymal stem cells and expressed the stem cell markers Oct-4, Nanog, Sox-2 and nestin. A massive lysosomal accumulation of cholesterol was observed only in cells isolated from NPC patients. After the induction of neural differentiation, remarkable morphologic changes were observed and cells became positive to markers of the neuronal lineage NeuN and MAP2. Differentiated cells from NPC patients displayed characteristic features of NPC disease, they showed intracellular accumulation of unesterified cholesterol and GM2 ganglioside and presented morphological differences with respect to cells derived from healthy donors.

In conclusion, we generated a human neuronal model of NPC disease through the induction of differentiation of stem cells obtained from patient’s easily accessible sources. The strategy described here may be applied to easily generate human neuronal models of other neurodegenerative diseases.

Cyclin-dependent kinases in brain development and disease

Cyclin-dependent kinase 5 (Cdk5) is a multifaceted serine/threonine kinase protein with important roles in the nervous system. Two related proteins, p35 and p39, activate Cdk5 upon direct binding. Over the past decade, Cdk5 activity has been demonstrated to regulate many events during brain development, including neuronal migration as well as axon and dendrite development. Recent evidence also suggests a pivotal role for Cdk5 in synaptic plasticity, behavior, and cognition. Dysfunction of Cdk5 has been implicated in a number of neurological disorders and neurodegenerative diseases including Alzheimer's disease, amyotrophic lateral sclerosis, Niemann-Pick type C disease, and ischemia. Hyperactivation of Cdk5 due to the conversion of p35 to p25 by the calcium-dependent protease calpain during neurotoxicity also contributes to the pathological state. This review surveys recent literature surrounding Cdk5 in synaptic plasticity and homeostasis, with particular emphasis on Cdk5 kinase activity under neurodegenerative conditions.

Corneal alterations during combined therapy with cyclodextrin/allopregnanolone and miglustat in a knock-out mouse model of NPC1 disease

Background

Niemann Pick disease type C1 is a neurodegenerative disease caused by mutations in the NPC1 gene, which result in accumulation of unesterified cholesterol and glycosphingolipids in the endosomal-lysosomal system as well as limiting membranes. We have previously shown the corneal involvement in NPC1 pathology in form of intracellular inclusions in epithelial cells and keratocytes. The purpose of the present study was to clarify if these inclusions regress during combined substrate reduction- and by-product therapy (SRT and BPT).

Methodology/Principal Findings

Starting at postnatal day 7 (P7) and thereafter, NPC1 knock-out mice (NPC1^−/−) and wild type controls (NPC1^+/+) were injected with cyclodextrin/allopregnanolone weekly. Additionally, a daily miglustat injection started at P10 until P23. Starting at P23 the mice were fed powdered chow with daily addition of miglustat. The sham group was injected with 0.9% NaCl at P7, thereafter daily starting at P10 until P23, and fed powdered chow starting at P23. For corneal examination, in vivo confocal laser-scanning microscopy (CLSM) was performed one day before experiment was terminated. Excised corneas were harvested for lipid analysis (HPLC/MS) and electron microscopy.

In vivo CLSM demonstrated a regression of hyperreflective inclusions in all treated NPC1^−/−mice. The findings varied between individual mice, demonstrating a regression, ranging from complete absence to pronounced depositions. The reflectivity of inclusions, however, was significantly lower when compared to untreated and sham-injected NPC1^−/− mice. These confocal findings were confirmed by lipid analysis and electron microscopy. Another important CLSM finding revealed a distinct increase of mature dendritic cell number in corneas of all treated mice (NPC1^−/− and NPC1^+/+), including sham-treated ones.

Conclusions/Significance

The combined substrate reduction- and by-product therapy revealed beneficial effects on the cornea. In vivo CLSM is a non-invasive tool to monitor disease progression and treatment effects in NPC1 disorder.

Lysosomal compromise and brain dysfunction: examining the role of neuroaxonal dystrophy

Lysosomal diseases are a family of over 50 disorders caused by defects in proteins critical for normal function of the endosomal/lysosomal system and characterized by complex pathogenic cascades involving progressive dysfunction of many organ systems, most notably the brain. Evidence suggests that compromise in lysosomal function is highly varied and leads to changes in multiple substrate processing and endosomal signalling, in calcium homoeostasis and endoplasmic reticulum stress, and in autophagocytosis and proteasome function. Neurons are highly vulnerable and show abnormalities in perikarya, dendrites and axons, often in ways seemingly unrelated to the primary lysosomal defect. A notable example is NAD (neuroaxonal dystrophy), which is characterized by formation of focal enlargements (spheroids) containing diverse organelles and other components consistent with compromise of retrograde axonal transport. Although neurons may be universally susceptible to NAD, GABAergic neurons, particularly Purkinje cells, appear most vulnerable and ataxia and related features of cerebellar dysfunction are a common outcome. As NAD is found early in disease and thus may be a contributor to Purkinje cell dysfunction and death, understanding its link to lysosomal compromise could lead to therapies designed to prevent its occurrence and thereby ameliorate cerebellar dysfunction.

Loss of amyloid precursor protein in a mouse model of Niemann-Pick type C disease exacerbates its phenotype and disrupts tau homeostasis

Niemann-Pick type C disease (NPC) is a lysosomal storage disorder which, at the cellular level, shows amyloid Aβ and tau pathologies comparable to those seen in the AD brain. Here, we have investigated, in a mouse model of NPC, the impact of removing the source of Aβ, namely APP, on the disease phenotype and on the expression levels and phosphorylation patterns of tau. We reasoned that removing APP from the NPC brain might help to unveil its impact on the disease phenotype and shed light on the mechanisms governing the interaction, both physiological and pathological, between APP function and tau homeostasis, at least in NPC. We show that, unexpectedly, loss of APP in NPC mice leads to poorer neuromuscular coordination and cumulative survival rates; exacerbation of their cholesterol abnormalities; higher levels of astrocytosis and dysregulation of tau homeostasis. Our results are consistent with a mechanism of neurodegeneration in the NPC and AD brains in which cholesterol dysregulation is a key early pathogenic event affecting tau homeostasis in parallel with, and independently of, amyloid accumulation.

Lipids on trial: the search for the offending metabolite in Niemann-Pick type C disease

Niemann-Pick disease type C is a complex lysosomal storage disorder caused by mutations in either the NPC1 or NPC2 genes that is characterized at the cellular level by the storage of multiple lipids, defective lysosomal calcium homeostasis and unique trafficking defects. We review the potential role of each of the individual storage lipids in initiating the pathogenic cascade and propose a model of NPC1 and NPC2 function based on the current knowledge.

Secondary lipid accumulation in lysosomal disease

Lysosomal diseases are inherited metabolic disorders caused by defects in a wide spectrum of lysosomal and a few non-lysosomal proteins. In most cases a single type of primary storage material is identified, which has been used to name and classify the disorders: hence the terms sphingolipidoses, gangliosidoses, mucopolysaccharidoses, glycoproteinoses, and so forth. In addition to this primary storage, however, a host of secondary storage products can also be identified, more often than not having no direct link to the primary protein defect. Lipids - glycosphingolipids and phospholipids, as well as cholesterol - are the most ubiquitous and best studied of these secondary storage materials. While in the past typically considered nonspecific and nonconsequential features of these diseases, newer studies suggest direct links between secondary storage and disease pathogenesis and support the view that understanding all aspects of this sequestration process will provide important insights into the cell biology and treatment of lysosomal disease.

Lentivector-mediated RNAi efficiently downregulates expression of murine TNF-alpha gene in vitro and in vivo

In order to explore the role of TNF-alpha in Niemann-Pick type C (NPC) disease, lentiviral-delivered RNA interference (RNAi) was used to silence the expression of murine TNF-alpha gene in vitro and in npc mice. Interference efficiency of the lentivirus expressing TNF-alpha-siRNA, previously constructed with the concentration of 2 x 10(8) ifu/mL, was determined by RT-PCR and ELISA in BV-2 cells and astrocytes. At the same time, the constructed Lenti-TNF-alpha-siRNA was intracerebroventricularly infused into 4-week old npc mice for a 4-week period, and the mice were divided into 3 groups: Lenti-TNF-alpha-siRNA (n=6), control lentivirus (n=6), and NPC mice without any intervention (n=4). By using immunohistochemistry and real-time PCR, the down-regulation of the target genes was detected. The Lenti-TNF-alpha-siRNA downregulated the expression of murine TNF-alpha gene efficiently in vitro and the interference efficiency was 66.7%. Lentivirus could be expressed stably for long-term in the npc mice brain. Immunohistochemistry and real-time PCR revealed that, as compared with non-intervention group and Lenti-control group, Lenti-TNF-alpha-siRNA efficiently down-regulated the expression of murine TNF-alpha gene with the interference efficiency being 66.9%. TNF-alpha-siRNA down-regulated the expression of TNF-alpha gene in vitro and in vivo, which provided a potential tool for studying and treating neurodegenerative diseases and TNF-alpha-related diseases.

Mitogen-activated protein kinase activity may not be necessary for the neuropathology of Niemann-Pick type C mice

Hyperphosphorylation of neurofilament and tau, and formation of cytoskeletal lesions, are notable features of several human neurodegenerative diseases, including Niemann-Pick Disease Type C (NPC). Previous studies suggested that the MAPKs, extracellular signal regulated kinase 1 and 2 (ERK1/2) may play a significant role in this aspect of NPC. To test this idea, we treated npc mice with PD98059, a specific and potent inhibitor of MAPK activation. Although activity of ERK1/2 was inhibited by 40%, a 2-week intracerebroventricular infusion of PD98059 just prior to onset of cytoskeletal pathology and symptoms in npc mice did not delay or inhibit prominent hallmarks of NPC. Unexpectedly, ERK1/2 inhibition led to aggravation of tau hyperphosphorylation, particularly in oligodendroctyes, in a manner similar to that of certain human tauopathies. Our results suggest that ERK1/2 does not play a major role in NPC neuropathology, and therefore, that MAPK inhibition is unlikely to be a useful strategy for managing the disease.

Recent advances in elucidating Niemann-Pick C disease

Lysosomal sequestration of endocytosed LDL-derived cholesterol, premature and abnormal enrichment of cholesterol in trans Golgi cisternae and accompanying anomalies in intracellular sterol trafficking are the hallmark phenotypic features of the Niemann-Pick C (NPC) lesion. A variable severity of these alterations has been observed, with only partial correlation between clinical and biochemical phenotypes. NPC also affects the metabolism of sphingolipids, and other biochemical abnormalities have been reported. Occurrence of neurofibrillary tangles in the brain of patients with a slowly progressive course is a recent intriguing observation. Genetic heterogeneity was established by cell hybridization and linkage studies. The two complementation groups could not be distinguished from each other by clinical, cellular or biochemical criteria, suggesting that the two gene products may interact or function sequentially. The major (> 90% of patients) NPC1 gene was mapped to 18q11 and recently isolated by positional cloning. The cDNA sequence predicts a 1278-amino acid protein, with 13 to 16 possible transmembrane regions and a putative cholesterol-sensing domain. Two murine models of the disease involving the same gene are known. The murine cDNA and the npc(nih) mutation have been characterized. Described homologies of the NPC1 protein are in line with its putative involvement in cellular cholesterol traffic.

Lactosylceramide in lysosomal storage disorders: a comparative immunohistochemical and biochemical study

Immunohistochemical studies of the presence of lactosylceramide (LacCer) in lysosomal storage disorders (LSDs) were done using anti-LacCer monoclonal antibody of the CDw 17 type (clone MG-2). No sign of an association between LacCer and the lysosomal system in normal cells was observed, except for histiocytes active in phagocytosis. A comparative study of a group of LSDs showed a general tendency for LacCer to increase in storage cells in Niemann-Pick disease type C (NPC), and types A and B, GM1 gangliosidosis, acid lipase deficiency, glycogen storage disease type II and mucopolysaccharidoses. LacCer accumulated in storage cells despite normal activity of relevant lysosomal degrading enzymes. The accumulation of LacCer displayed variability within storage cell populations, and was mostly expressed in neurons in NPC. An absence of the increase in LacCer in storage cells above control levels was seen in neuronal ceroid lipofuscinoses (neurons and cardiocytes) and in Fabry disease. Gaucher and Krabbe cells showed significantly lower levels, or even the absence, of LacCer compared with control macrophages. Results of immunohistochemistry were corroborated by semiquantitative lipid thin-layer chromatography (TLC). It is suggested that different associations of LacCer with the lysosomal storage process may reflect differences in glycosphingolipid turnover induced by the storage-compromised lysosomal/endosomal system.

Cholesterol homeostasis in neurons and glial cells

Cholesterol is highly enriched in the brain compared to other tissues. Essentially all cholesterol in the brain is synthesized endogenously since plasma lipoproteins are unable to cross the blood-brain barrier. Cholesterol is transported within the central nervous system in the form of apolipoprotein E-containing lipoprotein particles that are secreted mainly by glial cells. Cholesterol is excreted from the brain in the form of 24-hydroxycholesterol. Apolipoprotein E and cholesterol have been implicated in the formation of amyloid plaques in Alzheimer's disease. In addition, the progressive neurodegenerative disorder Niemann-Pick C disease is characterized by defects in intracellular trafficking of cholesterol.

Pathological cholesterol metabolism fails to modify electrophysiological properties of afflicted neurones in Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a recessive inherited neurovisceral lipid storage disease characterized by progressive motor impairment and a loss of neurones including those integrated into the motor system. One of the key neuropathological findings is the intracellular accumulation of lysosomes enriched with free cholesterol. This accumulation is due to impaired transport proteins named NPC1 (approx. 95% of the cases) or NPC2 (approx. 5%) responsible for the transport of endocytosed cholesterol from lysomes to plasma membranes. The perturbed lipid-transport in NPC cells leads to an altered lipid composition of the plasma membrane. Available evidence suggests that the lipid matrix influences the electrophysical properties of ion channels in membranes. We therefore evaluated whether electrophysiological properties of NPC neurones differ from healthy neurones. Both, acute brain slices and primary neuronal cell cultures from wildtype and NPC mice, a well-established mouse model for the Niemann-Pick type C disease, were used for a comparison of electrophysiological properties like resting membrane potential, input resistance, action potential amplitudes and synaptic properties of the neurones. In addition we optically recorded the changes of intraneuronal calcium levels elicited by depolarization. Our results show that the characteristics of ion channels in NPC neurones do not differ significantly from wildtype neurones. We therefore conclude that gross alterations of the electrophysiological properties of neurones will probably not initiate or substantially contribute to the development of the motor impairment or other neurological signs of NPC.

Consequences of NPC1 and NPC2 loss of function in mammalian neurons

Genetic deficiency of NPC1 or NPC2 results in a devastating cholesterol-glycosphingolipidosis of brain and other organs known as Niemann-Pick type C (NPC) disease. While NPC1 is a transmembrane protein believed involved in retroendocytic shuttling of substrate(s) to the Golgi and possibly elsewhere in cells as part of an essential recycling/homeostatic control mechanism, NPC2 is a soluble lysosomal protein known to bind cholesterol. The precise role(s) of NPC1 and NPC2 in endosomal-lysosomal function remain unclear, nor is it known whether the two proteins directly interact as part of this function. The pathologic features of NPC disease, however, are well documented. Brain cells undergo massive intracellular accumulation of glycosphingolipids (lactosylceramide, glucosylceramide, GM2 and GM3 gangliosides) and cholesterol and concomitant distortion of neuron shape (meganeurite formation). In neurons from humans with NPC disease the metabolic defects and storage often lead to extensive growth of new, ectopic dendrites (possibly linked to ganglioside sequestration) as well as formation of neurofibrillary tangles (NFTs) (possibly linked to dysregulation of cholesterol metabolism). Other features of cellular pathology in NPC disease include fragmentation of the Golgi apparatus and neuroaxonal dystrophy, though reasons for these changes remain largely unknown. As the disease progresses, neurodegeneration is also apparent for neurons in some brain regions, particularly Purkinje cells of the cerebellum, but the basis of this selective neuronal vulnerability is unknown. The NPC1 protein is evolutionarily conserved with homologues reported in yeast to humans; NPC2 is reported in C. elegans to humans. While neurons in mammalian models of NPC1 and NPC2 diseases exhibit many changes that are remarkably similar to those in humans (e.g., endosomal/lysosomal storage, Golgi fragmentation, neuroaxonal dystrophy, neurodegeneration), a reduced degree of ectopic dendritogenesis and an absence of NFTs in these species suggest important differences in the way lower mammalian neurons respond to NPC1/NPC2 loss of function.

A Riddle Wrapped in a Mystery: Understanding Niemann-Pick Disease, Type C

BACKGROUND

Niemann-Pick disease, type C (NPC), is a lipid storage disease that may present at any age from fetal life to the seventh decade. Its protean manifestations include hepatic and pulmonary failure, as well as a range of progressive neuropsychiatric phenotypes. Late onset disease has been increasingly recognized as the biochemical diagnosis of NPC has been more widely applied.

REVIEW SUMMARY

The phenotypes, biochemical, and molecular bases of NPC are reviewed. Indistinguishable phenotypes are produced by mutations in two distinct genes, designated NPC 1 and NPC 2, that play key roles in the intracellular trafficking of lipids. The diagnosis of NPC is challenging as the characteristic vertical supranuclear gaze palsy is difficult to recognize, organomegaly is often absent, and standard biochemical screening studies are usually normal. Definitive diagnosis requires demonstration of the trafficking defect in cultured fibroblasts, supplemented in selected cases by genotyping. Animal studies have shown that inhibition of glycosphingolipid synthesis may delay the onset of disease and prolong survival; a human trial of this approach is underway.

CONCLUSIONS

NPC is a model for inborn errors of metabolism whose gene product mediates molecular trafficking rather than catabolizing macromolecules, as in classic lipid storage diseases. NPC should be considered in the differential diagnosis of progressive neurodegenerative disorders at any age. The astute clinician can provide great comfort to families afflicted by NPC by making an accurate diagnosis, notwithstanding the absence of definitive treatment.

Cholesterol storage and tau pathology in Niemann-Pick type C disease in the brain

Niemann-Pick type C disease is an inherited neurovisceral storage disorder with intracellular accumulation of cholesterol. In affected brains, many ballooned neurons are seen. Considerable nerve cell loss of unknown pathogenesis leads to neurological deterioration and dementia. Chemical examination of brains has failed to demonstrate increased levels of cholesterol. Using filipin fluorometry of neuronal cells in tissue slices, we found massive accumulation of cholesterol in neurons in four out of five human Niemann-Pick type C cases including adult patients. Neurofibrillary tangles composed of aggregates of the otherwise highly soluble protein tau were present in three Niemann-Pick type C cases and were also immunologically identical to those associated with Alzheimer's disease. However, only a thin slab of spinal cord or a tiny piece of isocortex was available for examination in the two cases without tangles. In a further semi-quantitative analysis of 576 neurons, we determined higher cholesterol content in tangle-bearing neurons than in adjacent tangle-free neurons. The association of cholesterol accumulation with neurofibrillary degeneration in Niemann-Pick type C disease and Alzheimer's disease awakens interest in the role of impaired cholesterol metabolism in the development of neurofibrillary tangles in both diseases.

Frontal lobe atrophy due to a mutation in the cholesterol binding protein HE1/NPC2

This is the first description of slowly progressive Niemann-Pick disease type C (NPC) without the typical lysosomal storage in bone marrow and viscera in two descendants of a group of 17th century French-Canadians. The index patient was a married 43-year-old woman with onset of dementia in her thirties, later followed by the development of ataxia and athetoid movements. Her autopsy disclosed frontal lobe atrophy, neurolysosomal storage with oligolamellar inclusion and tau-positive neurofibrillary tangles. Of the 119 family members screened, only a married 42-year-old sister displayed symptoms of a dementia. Both women displayed vertical supranuclear ophthalmoplegia; expressive aphasia; concrete, stimulus-bound, perseverative behavior; and impaired conceptualization and planning. Cultured fibroblasts showed decreased cholesterol esterification and positive filipin staining, but no mutation was detected in coding or promoter regions of the NPC1 gene using conformation sensitive gel electrophoresis and sequencing. Sequencing showed a homozygous gene mutation that is predicted to result in an amino acid substitution, V39M, in the cholesterol binding protein HE1 (NPC2). Adult-onset NPC2 with lysosomal storage virtually restricted to neurons represents a novel phenotypic and genotypic variant with diffuse cognitive impairment and focal frontal involvement described for the first time.

Cholesterol accumulates in cell bodies, but is decreased in distal axons, of Niemann-Pick C1-deficient neurons

Niemann-Pick type-C (NPC) disease is characterized by a progressive loss of neurons and an accumulation of unesterified cholesterol within the endocytic pathway. Unlike other tissues, however, NPC1-deficient brains do not accumulate cholesterol but whether or not NPC1-deficient neurons accumulate cholesterol is not clear. Therefore, as most studies on cholesterol homeostasis in NPC1-deficient cells have been performed in fibroblasts we have investigated cholesterol homeostasis in cultured murine sympathetic neurons lacking functional NPC1. These neurons did not display obvious abnormalities in growth or morphology and appeared to respond normally to nerve growth factor. Filipin staining revealed numerous cholesterol-filled endosomes/lysosomes in NPC1-deficient neurons and the mass of cholesterol in cell bodies was greater than in wild-type neurons. Surprisingly, however, the cholesterol content of NPC1-deficient and wild-type neurons as a whole was the same. This apparent paradox was resolved when the cholesterol content of NPC1-deficient distal axons was found to be less than of wild-type axons. Cholesterol sequestration in cell bodies did not depend on exogenously supplied cholesterol since the cholesterol accumulated before birth and did not disperse when neurons were cultured without exogenous cholesterol. The altered cholesterol distribution between cell bodies and axons suggests that transport of cholesterol, particularly that synthesized endogenously, from cell bodies to distal axons is impaired in NPC1-deficient neurons.

Niemann-Pick disease type C yields possible clue for why cerebellar neurons do not form neurofibrillary tangles

It is unknown why cerebellar neurons resist neurofibrillary tangle (NFT) formation. In Niemann-Pick disease Type C (NPC), NFT-mediated neurodegeneration occurs throughout brain, but the cerebellum degenerates conspicuously without NFT. To understand why, we have studied markers of NFT pathogenesis in cerebellum from 17 NPC cases, all having abundant NFT in forebrain. Remarkably, we found that NPC cerebella display several early markers of NFT formation, i.e., hyperphosphorylated tau and an array of cell cycle regulators, suggesting that cerebellar neurons in NPC undergo similar modifications as other neurons that develop NFT. However, cerebellar neurons are deficient in tau, the building block of NFT, and this may be one reason for their inability to form NFT. Even without NFT, cerebellar neurodegeneration may be triggered by the inappropriate activation of the cell cycle cdc2 kinase, and the npc-1 murine model provides an opportunity to test this hypothesis.

Deregulation of cdk5, hyperphosphorylation, and cytoskeletal pathology in the Niemann-Pick type C murine model

NPC-1 gene mutations cause Niemann-Pick type C (NPC), a neurodegenerative storage disease resulting in premature death in humans. Spontaneous mutation of the NPC-1 gene in mice generates a similar phenotype, usually with death ensuing by 12 weeks of age. Both human and murine NPC are characterized neuropathologically by ballooned neurons distended with lipid storage, axonal spheroid formation, demyelination, and widespread neuronal loss. To elucidate the biochemical mechanism underlying this neuropathology, we have investigated the phosphorylation of neuronal cytoskeletal proteins in the brains of npc-1 mice. A spectrum of antibodies against phosphorylated epitopes in neurofilaments (NFs) and MAP2 and tau were used in immunohistochemical and immunoblotting analyses of 4- to 12-week-old mice. Multiple sites in NFs, MAP2, and tau were hyperphosphorylated as early as 4 weeks of age and correlated with a significant increase in activity of the cyclin-dependent kinase 5 (cdk5) and accumulation of its more potent activator, p25, a proteolytic fragment of p35. At 5 weeks of age, the development of axonal spheroids was noted in the pons. p25 and cdk5 coaccumulated with hyperphosphorylated cytoskeletal proteins in axon spheroids. These various abnormalities escalated with each additional week of age, spreading to other regions of the brainstem, basal ganglia, cerebellum, and eventually, the cortex. Our data suggest that focal deregulation of cdk5/p25 in axons leads to cytoskeletal abnormalities and eventual neurodegeneration in NPC. The npc-1 mouse is a valuable in vivo model for determining how and when cdk5 becomes deregulated and whether cdk5 inhibitors would be useful in blocking NPC neurodegeneration.

Progressive neuronal loss in the ventral posterior lateral and medial nuclei of thalamus in Niemann-Pick disease type C mouse brain

Niemann-Pick disease type C (NP-C) disease is a progressive and fatal neurological disorder characterized by accumulation of cholesterol and glycosphingolipids in peripheral tissues and that of glycosphingolipids in the brain. A C57BL/KsJ-npc1(spm) mutant strain is a genetically authentic model of NP-C. This study investigated neuronal cell loss and lipid accumulation in the npc1(spm) mouse brain. Nissl-staining revealed abundant swollen neurons in the neocortex, piriform cortex, hippocampus and basal ganglia at 3-4 wk of age. In addition to loss of the Purkinje cells, we found a conspicuous cell loss in the ventral posterial lateral (VPL) and medial (VPM) nuclei of thalamus, which became apparent after 4-5 wk. Biochemical analyses revealed no increase of cholesterol in the lipid extracts whereas a substantial accumulation of cholesterol was detectable in most of the large neurons by filipin staining in the brain of homozygous mice. In contrast to the diffuse staining pattern in normal brains, the neuropils of the neurons in the brain of homozygous mice were stained in a punctate pattern. The ubiquitous accumulation excludes a direct role of cholesterol in the progressive neuronal loss in the Purkinje cell layer and in the VPL and VPM of the thalamus.

Deficient ferritin immunoreactivity in tissues from niemann-pick type C patients: extension of findings to fetal tissues, H and L ferritin isoforms, but also one case of the rare Niemann-Pick C2 complementation group

Previous studies employing rabbit polyclonal anti-human liver ferritin have shown an absence of L ferritin immunoreactivity in liver and spleen tissue from patients with Niemann-Pick disease type C1 (NPC1). The great majority of NPC cases is caused by defects of the NPC1 gene, and a minority by those of another (NPC2). In this study using polyclonal and monoclonal antibodies we show the deficiency of H and L ferritin isoforms in various NPC tissues, including fetal NPC1, not previously described. In particular, evidence is provided for deficiency in H and L ferritins in tissues, except lung, from a patient with Niemann-Pick disease type C2 (NPC2). The present findings indicate that H and L ferritins are deficient in both NPC types characterized by accumulation of unesterified cholesterol and additional metabolites in the endosomal/lysosomal system. We hypothesize that the lesions in NPC1 and NPC2 block the intracellular utilization not only of cholesterol, but also that of iron for the synthesis of cytosolic ferritin.

Lipid changes in Niemann-Pick disease type C brain: personal experience and review of the literature

Niemann-Pick disease type C (NPC) is a neurovisceral disorder characterized by lysosomal sequestration of endocytosed LDL-cholesterol, premature and abnormal enrichment of cholesterol in trans Golgi cisternae and accompanying anomalies in intracellular sterol trafficking. In addition to cholesterol, the NPC lesion has also been shown to impact the metabolism of sphingolipids. Lipids, more particularly glycolipids, were studied in brain tissue from eight cases with proven NPC, ranging from 21 fetal weeks to 19 years of age (one case with rapidly fatal neonatal cholestatic icterus, three cases with infantile neurological onset, one late infantile and two juvenile neurological cases). In gray matter, the concentrations of total cholesterol, sphingomyelin and total gangliosides were within the normal range in all cases. In white matter, a severe loss of galactosylceramide and other myelin lipids (including cholesterol) was prominent in patients with the neurological severe infantile form (levels similar to those in 6-8 month-old infants) or the late infantile form of the disease, but only a slight decrease was observed in patients with a juvenile neurological onset. Analysis of the ganglioside profiles and study of minor neutral glycolipids revealed striking abnormalities, although not present at the fetal stage. In cerebral cortex, gangliosides GM3 and GM2 showed a significant increase, 10-15 fold and 3-5-fold the normal level, respectively, with already some abnormalities in a 3-month-old patient. Except in the latter patient, a prominent storage of glucosylceramide, lactosylceramide and gangliotriaosylceramide (asialo-GM2) was observed, with 10-50-fold increases from the normal concentration. The fatty acid composition of these glycolipids suggests that they have a neuronal origin. A slight increase of globotriaosyl- and globotetraosylceramide and of more complex neutral glycolipids also occurred. While ganglioside changes were essentially similar in gray and white matter, changes of the neutral glycolipids were only minimal in the latter. Our data are in good accordance with previous studies and provide additional information. They emphasize that, apart a varying demyelinating process (most pronounced in children with a severe infantile neurological form) brain lipids abnormalities are essentially located to the gray matter. They confirm and give more precise information on the glycolipid nature of the neuronal storage, and establish that a similar type of changes occurs in the different neurological forms of the disease. Yet, our study indicates that glycolipid changes in brain do not occur before a few months after birth, possibly at a period concomitant with the onset of neurological symptoms, in contrast to the very early glycolipid abnormalities observed in non-neural organs. Glycolipid changes rather similar to those seen in NPC brain, in particular for gangliosides, have been described for other lysosomal disorders such as Niemann-Pick type A and mucopolysaccharidoses. The glucosyl-and lactosylceramide accumulation, however, is more striking in NPC, especially taking into account that there is no other known storage in NPC brain. Some neuropathological changes, such as ectopic neurites, could be related to the glycolipid changes. Metabolic studies in cultured fibroblasts combined to the observation that no lipids other than glycolipids accumulate in brain suggest that the NPC gene products possibly participate in intracellular transport or regulate metabolism of glycolipids.

Infrared Spectroscopic Imaging of the Biochemical Modifications Induced in the Cerebellum of the Niemann-Pick type C Mouse

We have applied Fourier transform infrared (IR) spectroscopic imaging to the investigation of the neuropathologic effects of a genetic lipid storage disease, Niemann-Pick type C (NPC). Tissue sections both from the cerebella of a strain of BALB/c mice that demonstrated morphology and pathology of the human disease and from control animals were used. These samples were analyzed by standard histopathological procedures as well as this new IR imaging approach. The IR absorbance images exhibit contrast based on biochemical variations and allow for the identification of the cellular layers within the tissue samples. Furthermore, these images provide a qualitative description of the localized biochemical differences existing between the diseased and control tissue in the absence of histological staining. Statistical analyses of the IR spectra extracted from individual cell layers of the imaging data sets provide concise quantitative descriptions of these biochemical changes. The results indicate that lipid is depleted specifically in the white matter of the NPC mouse in comparison to the control samples. Minor differences were noted for the granular layers, but no significant differences were observed in the molecular layers of the cerebellar tissue. These changes are consistent with significant demyelination within the cerebellum of the NPC mouse. © 1999 Society of Photo-Optical Instrumentation Engineers.

Niemann-Pick C disease: cholesterol handling gone awry

Niemann-Pick C disease (NPC) is a debilitating, recessive disorder in humans that causes unrelenting neurological deterioration and is complicated by the presence of lipid-laden foamy cells in the major organs of the body. NPC fibroblasts cultured with an excess of low density lipoprotein (LDL) abnormally sequester cholesterol in their lysosomes. Biochemical analyses of NPC cells suggest an impairment in the intracellular transport of cholesterol to post-lysosomal destinations occurs in NPC. The recent identification of the NPC gene, NPC1, provides a definitive diagnosis of the disease and a means of studying this key component of intracellular cholesterol transport and homeostasis.

Increased levels of GM2 ganglioside in fibroblasts from a patient with juvenile Niemann-Pick disease type C

A 15-year-old boy was suffering from splenomegaly and a 10-year history of a neurologic disorder that included mental retardation, vertical supranuclear gaze palsy, dysarthria, ataxia, and dystonia. Bone marrow aspirates revealed foamy cells with storage materials which were positive with filipin staining. Cultured skin fibroblasts derived from the patient showed moderate loss of sphingomyelinase activity and the impairment of cholesterol esterification. The characteristic clinical presentations and typical histochemical findings of this patient met the diagnostic criteria of Niemann-Pick disease type C (NPC). In the fibroblasts from the patient, there was an accumulation of GM2 ganglioside around their cytoplasms. Increased levels of glycolipids. including GM2 ganglioside are reported in the cerebral cortex of NPC, but not in the fibroblasts. The fibroblasts derived from NPC may reflect the abnormal metabolism of glycolipids in the central nervous system of NPC.

Psychosis as a presentation of physical disease in adolescence: a case of Niemann-Pick disease, type C

This study reports the case of a 16-year-old male who presented with a history of prominent psychotic symptoms and paranoid delusions which overshadowed subtle signs and symptoms of cognitive and motor dysfunction. Intensive neurobehavioral and biochemical investigations eventually led to the diagnosis of Niemann-Pick disease, type C (NPC), an autosomal recessively inherited storage disease that is associated with the accumulation of cholesterol in lysosomes and difficulties in the processing of exogenously derived cholesterol. Clues to the presence of a neurological disorder included: a history of insidiously declining academic and athletic performance which antedated the onset of psychosis; abnormalities on mental status examination, including psychomotor slowing, memory difficulties, and impairment of higher attentional functions; physical findings of subtle downgaze impairment, mild symmetrical hyperreflexia, and lower-extremity hypertonia with flexor plantar responses, marked impairment of upper-extremity rapid alternating movements, action tremor, and bilateral posturing with stress gait maneuvers. This case demonstrates the importance of careful and persistent neurodiagnostic evaluation in adolescents with psychotic presentations, particularly when cognitive and motor deterioration is suspected, and even when head CT and MRI scans are judged to be normal.

Peripheral nerve pathology in Niemann-Pick type C mouse

The sciatic nerve of the mouse mutant with Niemann-Pick type C disease (NPC mouse) was investigated using light and electron microscopy, and teased-fiber preparations. As early as postnatal day 20, when clinical symptoms were not yet apparent, focal paranodal swellings with an accumulation of small myelin figures in the Schwann cell cytoplasm were noted. These paranodal changes were more pronounced in the distal segment and became progressively conspicuous with increasing age. The morphometric analysis revealed a hypomyelination of large myelinated fibers in the NPC nerves at 70 days, whereas an essentially similar histogram pattern was noted in both control and NPC nerves at 20 days, suggesting progressively defective utilization of cholesterol in the NPC nerves with age. Intraxonal accumulation of dense bodies was noted in older mice, but no segmental demyelination or Wallerian type of axonal degeneration was observed at any age. The changes noted in the paranodal regions in the NPC mouse closely resemble those found in rats treated with an inhibitor of cholesterol biosynthesis, as well as those seen in remodeling fibers during an early stage of peripheral nerve development. Thus, the morphological changes seen in the sciatic nerve of the NPC mouse may be an expression of perturbation in myelin maintenance as a result of defective cholesterol metabolism.

Magnetic resonance spectroscopy in Niemann-Pick disease type C: correlation with diagnosis and clinical response to cholestyramine and lovastatin

Niemann-Pick type C is an autosomal-recessive, neurovisceral storage disorder that results from defective cholesterol esterification. Cholesterol-lowering agents have been demonstrated to decrease hepatic lipids in Niemann-Pick type C patients. The objective was to determine the effects of cholesterol-lowering agents on neurologic features and to develop a noninvasive method of monitoring clinical response. A 9-month-old boy with progressive hepatosplenomegaly and neurodevelopmental delay was studied. Water-suppressed proton magnetic resonance spectra from a supraventricular volume of central white and gray matter revealed an abnormal lipid signal. The patient was treated with cholesterol-lowering agents (i.e., cholestyramine, lovastatin). Repeat standardized neurodevelopmental assessments (Peabody and Griffith scales) at 13 and 19 months were normal and magnetic resonance spectra no longer detected the previously observed lipid resonance. Early treatment of Niemann-Pick type C patients with cholesterol-lowering agents appeared to have short-term beneficial effects. Magnetic resonance spectra provided a noninvasive means of monitoring CNS response.

Neurological manifestations of Niemann-Pick disease type C in cats

Seven Domestic shorthair cats with a lysosomal storage disorder analogous to human Niemann-Pick disease type C, from a breeding colony were studied to characterize the neurological manifestations of this disorder. Affected cats were identified by means of liver biopsies at 4 to 6 weeks of age. Neurological examinations were performed at 2 week intervals from the onset of clinical signs. All cats displayed signs referrable to the cerebellum, with a subtle intention tremor noticed initially at 8 to 12 weeks of age; the disease was rapidly progressive. The tremor became more pronounced, menace response was lost, and severe dysmetria and ataxia developed. Three cats also had signs referrable to other areas of the central nervous system. Cats died or were euthanized between 12 and 43 weeks of age. Pathological findings included accumulation of substrate within neurons throughout the central nervous system, and axonal spheroid formation. The clinical and pathological findings in these cats are comparable to those in the human form of the disease.

Nerve biopsy findings in Niemann-Pick type II (NPC)

The severe infantile form of Niemann-Pick disease type II was diagnosed in a 4-year-old girl and confirmed by demonstrating in cultured skin fibroblasts a deficiency of low-density lipoprotein-stimulated cholesterol ester synthesis of < 5% of normal. Electrodiagnostic studies revealed changes of a predominantly demyelinating motor and sensory polyneuropathy. Light microscope and ultrastructural examination of a peroneal nerve biopsy showed unique changes. Compacted myelin sheaths were disproportionately thin with marked globular irregularities in single teased nerve fibres and evidence of chronic demyelination. The majority of axons were preserved but axonal spheroids and cytoskeletal abnormalities akin to neuroaxonal dystrophy were noted. Membrane-bound multi-lobulated lysosomal inclusions of floccular and electron-dense material were present in Schwann cells (SC), endoneurial fibroblasts, macrophages, pericytes and endothelial cells. SC of myelinated fibres were stuffed with whorls of concentric osmiophilic membraneous profiles and electron-lucent material. The findings are diagnostic and differ from those of classical Niemann-Pick disease.

Cerebellar degeneration in the Niemann-Pick type C mouse

Chronological morphological changes and topographical distribution of degenerating Purkinje cells were studied in the murine model of Niemann-Pick disease type C (NPC mouse). Loss of Purkinje cells can be detected in the anterior vermis as early as 60 days of age, coinciding with early neurological signs, and progressed to total absence in the entire hemisphere and vermis with exception of nodules. Ultrastructurally, concentric lamellar inclusions were detected in the perikarya of degenerating Purkinje cells as well as in the focally enlarged branching points of their dendrites. Calbindin immunocytochemistry demonstrated dendritic pathology characterized by irregular contour of dendritic trees and decreased number of dendritic spines. Ubiquitin immunoreactivity revealed granular reaction products in the perikarya, dendrites and axons of Purkinje cells. Our studies demonstrated unique pathological features of Purkinje cells that involve perikarya, dendrites and axons in the NPC mouse.