The complexity of a monogenic neurodegenerative disease: More than two decades of therapeutic driven research into Niemann-Pick type C disease

Endothelial and neuronal engagement by AAV-BR1 gene therapy alleviates neurological symptoms and lipid deposition in a mouse model of Niemann-Pick type C2

BACKGROUND

Patients with the genetic disorder Niemann-Pick type C2 disease (NP-C2) suffer from lysosomal accumulation of cholesterol causing both systemic and severe neurological symptoms. In a murine NP-C2 model, otherwise successful intravenous Niemann-Pick C2 protein (NPC2) replacement therapy fails to alleviate progressive neurodegeneration as infused NPC2 cannot cross the blood-brain barrier (BBB). Genetic modification of brain endothelial cells (BECs) is thought to enable secretion of recombinant proteins thereby overcoming the restrictions of the BBB. We hypothesized that an adeno-associated virus (AAV-BR1) encoding the Npc2 gene could cure neurological symptoms in Npc2-/- mice through transduction of BECs, and possibly neurons via viral passage across the BBB.

METHODS

Six weeks old Npc2-/- mice were intravenously injected with the AAV-BR1-NPC2 vector. Composite phenotype scores and behavioral tests were assessed for the following 6 weeks and visually documented. Post-mortem analyses included gene expression analyses, verification of neurodegeneration in Purkinje cells, determination of NPC2 transduction in the CNS, assessment of gliosis, quantification of gangliosides, and co-detection of cholesterol with NPC2 in degenerating neurons.

RESULTS

Treatment with the AAV-BR1-NPC2 vector improved motor functions, reduced neocortical inflammation, and preserved Purkinje cells in most of the mice, referred to as high responders. The vector exerted tropism for BECs and neurons resulting in a widespread NPC2 distribution in the brain with a concomitant reduction of cholesterol in adjacent neurons, presumably not transduced by the vector. Mass spectrometry imaging revealed distinct lipid alterations in the brains of Npc2-/- mice, with increased GM2 and GM3 ganglioside accumulation in the cerebellum and hippocampus. AAV-BR1-NPC2 treatment partially normalized these ganglioside distributions in high responders, including restoration of lipid profiles towards those of Npc2+/+ controls.

CONCLUSION

The data suggests cross-correcting gene therapy to the brain via delivery of NPC2 from BECs and neurons.

Structural and biochemical analysis of ligand binding in yeast Niemann-Pick type C1-related protein

In eukaryotes, integration of sterols into the vacuolar/lysosomal membrane is critically dependent on the Niemann-Pick type C (NPC) system. The system consists of an integral membrane protein, called NCR1 in yeast, and NPC2, a luminal soluble protein that transfers sterols to the N-terminal domain (NTD) of NCR1 before membrane integration. Both proteins have been implicated in sterol homeostasis of yeast and humans. Here, we investigate sterol and lipid binding of the NCR1/NPC2 transport system and determine crystal structures of the sterol binding NTD. The NTD binds both ergosterol and cholesterol, with nearly identical conformations of the binding pocket. Apart from sterols, the NTD can also bind fluorescent analogs of phosphatidylinositol, phosphatidylcholine, and phosphatidylserine, as well as sphingosine and ceramide. We confirm the multi-lipid scope of the NCR1/NPC2 system using photo-crosslinkable and clickable lipid analogs, namely, pac-cholesterol, pac-sphingosine, and pac-ceramide. Finally, we reconstitute the transfer of pac-sphingosine from NPC2 to the NTD in vitro. Collectively, our results support that the yeast NPC system can work as versatile machinery for vacuolar homeostasis of structurally diverse lipids, besides ergosterol.

Clinical presentation and molecular genetics of Iranian patients with Niemann-pick type C disease and report of 6 NPC1 gene novel variants: A case series

Niemann Pick Type C disease is a rare and progressive neurodegenerative lysosomal storage disorder caused by autosomal recessive mutations in the NPC1 and NPC2 genes. It is characterized by the accumulation of multiple lipid species in the endolysosomal compartment, leading to neurodegeneration and involvement of the liver, spleen, and lungs. Niemann Pick Type C has a wide range of presentations and severities at different ages with different progression rates. According to the Human Gene Mutation Database, to date, 486 disease-causing mutations in the highly polymorphic NPC1 gene and >20 mutations in the NPC2 have been reported. In the present study, we described the clinical, biochemical, and molecular profiles of 18 Iranian patients with Niemann-Pick Type C disease. Also, we describe six novel variants of the NPC1 gene, to our knowledge, not reported to date.

Endo-lysosomal dysfunction and neuronal-glial crosstalk in Niemann-Pick type C disease

Niemann-Pick type C (NPC) disease is a rare progressive lysosomal lipid storage disorder that manifests with a heterogeneous spectrum of clinical syndromes, including visceral, neurological and psychiatric symptoms. This monogenetic autosomal recessive disease is largely caused by mutations in the NPC1 gene, which controls intracellular lipid homeostasis. Vesicle-mediated endo-lysosomal lipid trafficking and non-vesicular lipid exchange via inter-organelle membrane contact sites are both regulated by the NPC1 protein. Loss of NPC1 function therefore triggers intracellular accumulation of diverse lipid species, including cholesterol, glycosphingolipids, sphingomyelin and sphingosine. The NPC1-mediated dysfunction of lipid transport has severe consequences for all brain cells, leading to neurodegeneration. Besides the cell-autonomous contribution of neuronal NPC1, aberrant NPC1 signalling in other brain cells is critical for the pathology. We discuss here the importance of endo-lysosomal dysfunction and a tight crosstalk between neurons, oligodendrocytes, astrocytes and microglia in NPC pathology. We strongly believe that a cell-specific rescue may not be sufficient to counteract the severity of the NPC pathology, but targeting common mechanisms, such as endo-lysosomal and lipid trafficking dysfunction, may ameliorate NPC pathology. This article is part of a discussion meeting issue 'Understanding the endo-lysosomal network in neurodegeneration'.

Investigating the Effect of Aspirin on apoAI-Induced ATP Binding Cassette Transporter 1 Protein Expression and Cholesterol Efflux in Human Astrocytes

Background

Neurons need a high amount of cholesterol to maintain the stability of their membrane-rich structures. Astrocytes synthesize and distribute cholesterol to neurons, and ABCA1 is a key mediator of cholesterol efflux to generate HDL for cholesterol transport in the brain. Several studies imply the effect of aspirin on ABCA1 expression in peripheral cells such as macrophages. Here, we compared the effect of aspirin with apoA-I on ABCA1 protein expression and cholesterol efflux in human astrocytes.

Materials and Methods

Human astrocytes were cultured, and the effects of aspirin on the expression and protein levels of ABCA1 were investigated through RT-PCR and Western blot analysis. Additionally, the effect of co-treatment with apoA-I and aspirin on ABCA1 protein level and cholesterol efflux was evaluated.

Results

Dose and time-course experiments showed that the maximum effect of aspirin on ABCA1 expression occurred at a concentration of 0.5 mM after 12 h of incubation. RT-PCR and western blot data showed that aspirin upregulates ABCA1 expression by up to 4.7-fold and its protein level by 67%. Additionally, co-treatment with aspirin and apoA-I increased cholesterol release from astrocytes, indicating an additive effect of aspirin on apoAI-mediated cholesterol efflux.

Conclusions

The results suggest a potential role of aspirin in increasing ABCA1 expression and cholesterol efflux in astrocytes, similar to the effect of apoA-I. This indicates that aspirin could potentially regulate brain cholesterol balance and can be considered in certain neurological diseases, in particular in some neurological disorders related to cholesterol accumulation such as Alzheimer's disease.

Long-term administration of intravenous Trappsol® Cyclo™ (HP-β-CD) results in clinical benefits and stabilization or slowing of disease progression in patients with Niemann-Pick disease type C1: Results of an international 48-week Phase I/II trial

Background

Niemann-Pick disease type C (NPC) is a rare, fatal, pan-ethnic, autosomal recessive lysosomal storage disease characterized by progressive major organ failure and neurodegeneration. Preclinical studies confirmed a critical role of systemically administered hydroxypropyl-β-cyclodextrin (HP-β-CD; Trappsol® Cyclo™) in cholesterol metabolism and homeostasis in peripheral tissues of the body, including the liver, and in the central nervous system (CNS). Herein, the pharmacokinetics (PK), safety, and efficacy of HP-β-CD, and biomarkers of NPC were assessed in pediatric and adult patients with NPC1.

Methods

This was a multicenter, Phase I/II, randomized, double-blind, parallel-group, 48-week study (ClinicalTrials.gov identifier NCT02912793) to compare the PK of three different single intravenous (IV) doses of HP-β-CD in pediatric and adult patients with NPC1 and to evaluate the efficacy and tolerability of three different dosages of HP-β-CD in patients with NPC1 after long-term treatment. Twelve patients aged at least 2 years (2-39 years of age) with a confirmed diagnosis of NPC1 were randomized to receive one of three IV doses of HP-β-CD (1500 mg/kg, 2000 mg/kg, or 2500 mg/kg) every 2 weeks for 48 weeks. All patients received HP-β-CD; there was no placebo or other control. PK testing of plasma and cerebrospinal fluid (CSF) was at set times after the first infusion. Pharmacodynamic assessments included biomarkers of cholesterol metabolism (synthesis and breakdown products), N-palmitoyl-O-phosphocholineserine (PPCS), and specific biomarkers of CSF neurodegeneration (including total Tau), CNS inflammation (glial fibrillary acidic protein [GFAP] and tumor necrosis factor α [TNFα]), CNS cholesterol metabolism (24S-hydroxycholesterol) and inflammatory markers. Efficacy measures included clinical disease severity, neurologic symptoms, and clinical impressions of improvement. Safety assessment included physical examination, vital signs, clinical safety laboratory assessment and adverse events (AEs).

Results

Nine patients completed the study, 2 in the 1500 mg/kg group, 4 in the 2000 mg/kg group and 3 in the 2500 mg/kg group. Three patients (all in the 1500 mg/kg group) discontinued the study because of either physician decision/site Principal Investigator (PI) discretion, withdrawal by subject/patient/parent/guardian, or other non-safety reasons. In 5 patients who underwent serial lumbar punctures, HP-β-CD was detected in the CSF. Of the 9 patients who completed the study, 8 (88.9%) improved in at least two domains of the 17-Domain Niemann-Pick disease Type C-Clinical Severity Scale (17D-NPC-CSS), and 6 of these patients improved in at least one domain viewed by patients and their caregivers to be key to quality of life, namely, speech, swallow, fine and gross motor skills, and cognition. Of the 9 patients who completed the study, 7 were viewed by their treating physicians as having improved to some degree at the end of the study, and 2 remained stable; both outcomes are highly relevant in a progressive neurodegenerative disease. Some patients and families reported improvement in quality of life.All three doses of HP-β-CD were well tolerated overall, with most treatment-emergent adverse events transient, mild-to-moderate in nature, and considered by the site PIs to be not related to study drug.

Interpretation

This 48-week trial is the longest to date to evaluate the safety, tolerability, and efficacy across multiple clinical endpoints of IV administration of Trappsol® Cyclo™ (HP-β-CD) in NPC1 patients. In pediatric and adult patients with NPC, Trappsol® Cyclo™ IV improved clinical signs and symptoms and was generally well tolerated. The findings presented here demonstrate a favorable benefit-risk profile and support the global pivotal trial now underway to evaluate the long-term treatment benefits and the potential of Trappsol® Cyclo™ as a disease-modifying treatment in this patient population.

Identification and characterization of protein interactions with the major Niemann-Pick type C disease protein in yeast reveals pathways of therapeutic potential

Niemann-Pick type C (NP-C) disease is a rare lysosomal storage disease caused by mutations in NPC1 (95% cases) or NPC2 (5% cases). These proteins function together in cholesterol egress from the lysosome, whereby upon mutation, cholesterol and other lipids accumulate causing major pathologies. However, it is not fully understood how cholesterol is transported from NPC1 residing at the lysosomal membrane to the endoplasmic reticulum (ER) and plasma membrane. The yeast ortholog of NPC1, Niemann-Pick type C-related protein-1 (Ncr1), functions similarly to NPC1; when transfected into a mammalian cell lacking NPC1, Ncr1 rescues the diagnostic hallmarks of cholesterol and sphingolipid accumulation. Here, we aimed to identify and characterize protein-protein interactions (PPIs) with the yeast Ncr1 protein. A genome-wide split-ubiquitin membrane yeast two-hybrid (MYTH) protein interaction screen identified 11 ER membrane-localized, full-length proteins interacting with Ncr1 at the lysosomal/vacuolar membrane. These highlight the importance of ER-vacuole membrane interface and include PPIs with the Cyb5/Cbr1 electron transfer system, the ceramide synthase complex, and the Sec61/Sbh1 protein translocation complex. These PPIs were not detected in a sterol auxotrophy condition and thus depend on normal sterol metabolism. To provide biological context for the Ncr1-Cyb5 PPI, a yeast strain lacking this PPI (via gene deletions) exhibited altered levels of sterols and sphingolipids including increased levels of glucosylceramide that mimic NP-C disease. Overall, the results herein provide new physical and genetic interaction models to further use the yeast model of NP-C disease to better understand human NP-C disease.

The Niemann-Pick type diseases – A synopsis of inborn errors in sphingolipid and cholesterol metabolism

Disturbances of lipid homeostasis in cells provoke human diseases. The elucidation of the underlying mechanisms and the development of efficient therapies represent formidable challenges for biomedical research. Exemplary cases are two rare, autosomal recessive, and ultimately fatal lysosomal diseases historically named "Niemann-Pick" honoring the physicians, whose pioneering observations led to their discovery. Acid sphingomyelinase deficiency (ASMD) and Niemann-Pick type C disease (NPCD) are caused by specific variants of the sphingomyelin phosphodiesterase 1 (SMPD1) and NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2) genes that perturb homeostasis of two key membrane components, sphingomyelin and cholesterol, respectively. Patients with severe forms of these diseases present visceral and neurologic symptoms and succumb to premature death. This synopsis traces the tortuous discovery of the Niemann-Pick diseases, highlights important advances with respect to genetic culprits and cellular mechanisms, and exposes efforts to improve diagnosis and to explore new therapeutic approaches.

Heat shock protein amplification improves cerebellar myelination in the Npc1nih mouse model

BACKGROUND

Niemann-Pick disease type C (NPC) is a rare prematurely fatal lysosomal lipid storage disease with limited therapeutic options. The prominent neuropathological hallmarks include hypomyelination and cerebellar atrophy. We previously demonstrated the efficacy of recombinant human heat shock protein 70 (rhHSP70) in preclinical models of the disease. It reduced glycosphingolipid levels in the central nervous system (CNS), improving cerebellar myelination and improved behavioural phenotypes in Npc1^nih (Npc1^-/-) mice. Furthermore, treatment with arimoclomol, a well-characterised HSP amplifier, attenuated lysosomal storage in NPC patient fibroblasts and improved neurological symptoms in Npc1^-/- mice. Taken together, these findings prompted the investigation of the effects of HSP amplification on CNS myelination.

METHODS

We administered bimoclomol daily or rhHSP70 6 times per week to Npc1^-/- (BALB/cNctr-Npc1^m1N/J, also named Npc1^nih) mice by intraperitoneal injection from P7 through P34 to investigate the impact on CNS myelination. The Src-kinase inhibitor saracatinib was administered with/without bimoclomol twice daily to explore the contribution of Fyn kinase to bimoclomol's effects.

FINDINGS

Treatment with either bimoclomol or rhHSP70 improved myelination and increased the numbers of mature oligodendrocytes (OLs) as well as the ratio of active-to-inactive forms of phosphorylated Fyn kinase in the cerebellum of Npc1^-/- mice. Additionally, treatment with bimoclomol preserved cerebellar weight, an effect that was abrogated when co-administered with saracatinib, an inhibitor of Fyn kinase. Bimoclomol-treated mice also exhibited increased numbers of immature OLs within the cortex.

INTERPRETATION

These data increase our understanding of the mechanisms by which HSP70 regulates myelination and provide further support for the clinical development of HSP-amplifying therapies in the treatment of NPC.

FUNDING

Funding for this study was provided by Orphazyme A/S (Copenhagen, Denmark) and a Pathfinder Award from The Wellcome Trust.

mRNA Treatment Rescues Niemann-Pick Disease Type C1 in Patient Fibroblasts

Messenger RNA (mRNA) holds great potential as a disease-modifying treatment for a wide array of monogenic disorders. Niemann-Pick disease type C1 (NP-C1) is an ultrarare monogenic disease that arises due to loss-of-function mutations in the NPC1 gene, resulting in the entrapment of unesterified cholesterol in the lysosomes of affected cells and a subsequent reduction in their capacity for cholesterol esterification. This causes severe damage to various organs including the brain, liver, and spleen. In this work, we describe the use of NPC1-encoded mRNA to rescue the protein insufficiency and pathogenic phenotype caused by biallelic NPC1 mutations in cultured fibroblasts derived from an NP-C1 patient. We first evaluated engineering strategies for the generation of potent mRNAs capable of eliciting high protein expression across multiple cell types. We observed that "GC3" codon optimization, coupled with N1-methylpseudouridine base modification, yielded an mRNA that was approximately 1000-fold more potent than wild-type, unmodified mRNA in a luciferase reporter assay and consistently superior to other mRNA variants. Our data suggest that the improved expression associated with this design strategy was due in large part to the increased secondary structure of the designed mRNAs. Both codon optimization and base modification appear to contribute to increased secondary structure. Applying these principles to the engineering of NPC1-encoded mRNA, we observed a normalization in NPC1 protein levels after mRNA treatment, as well as a rescue of the mutant phenotype. Specifically, mRNA treatment restored the cholesterol esterification capacity of patient cells to wild-type levels and induced a significant reduction in both unesterified cholesterol levels (>57% reduction compared to Lipofectamine-treated control in a cholesterol esterification assay) and lysosome size (157 μm² reduction compared to Lipofectamine-treated control). These findings show that engineered mRNA can correct the deficit caused by NPC1 mutations. More broadly, they also serve to further validate the potential of this technology to correct diseases associated with loss-of-function mutations in genes coding for large, complex, intracellular proteins.

Discovering monogenic patients with a confirmed molecular diagnosis in millions of clinical notes with MonoMiner

PURPOSE

Cohort building is a powerful foundation for improving clinical care, performing biomedical research, recruiting for clinical trials, and many other applications. We set out to build a cohort of all monogenic patients with a definitive causal gene diagnosis in a 3-million patient hospital system.

METHODS

We define a subset (4461) of OMIM diseases that have at least 1 known monogenic causal gene. We then introduce MonoMiner, a natural language processing framework to identify molecularly confirmed monogenic patients from free-text clinical notes.

RESULTS

We show that ICD-10-CM codes cover only a fraction of monogenic diseases and that even where available, ICD-10-CM code‒based patient retrieval offers 0.14 precision. Searching by causal gene symbol offers great recall but has an even worse 0.07 precision. MonoMiner achieves 6 to 11 times higher precision (0.80), with 0.87 precision on disease diagnosis alone, tagging 4259 patients with 560 monogenic diseases and 534 causal genes, at 0.48 recall.

CONCLUSION

MonoMiner enables the discovery of a large, high-precision cohort of patients with monogenic diseases with an established molecular diagnosis, empowering numerous downstream uses. Because it relies solely on clinical notes, MonoMiner is highly portable, and its approach is adaptable to other domains and languages.

Repurposing Dipyridamole in Niemann Pick Type C Disease: A Proof of Concept Study

Niemann Pick type C disease (NPC) is a rare disorder characterized by lysosomal lipid accumulation that damages peripheral organs and the central nervous system. Currently, only miglustat is authorized for NPC treatment in Europe, and thus the identification of new therapies is necessary. The hypothesis addressed in this study is that increasing adenosine levels may represent a new therapeutic approach for NPC. In fact, a reduced level of adenosine has been shown in the brain of animal models of NPC; moreover, the compound T1-11, which is able to weakly stimulate A_2A receptor and to increase adenosine levels by blocking the equilibrative nucleoside transporter ENT1, significantly ameliorated the pathological phenotype and extended the survival in a mouse model of the disease. To test our hypothesis, fibroblasts from NPC1 patients were treated with dipyridamole, a clinically-approved drug with inhibitory activity towards ENT1. Dipyridamole significantly reduced cholesterol accumulation in fibroblasts and rescued mitochondrial deficits; the mechanism elicited by dipyridamole relies on activation of the adenosine A_2AR subtype subsequent to the increased levels of extracellular adenosine due to the inhibition of ENT1. In conclusion, our results provide the proof of concept that targeting adenosine tone could be beneficial in NPC.

Cholesterol synthesis inhibition or depletion in axon regeneration

Cholesterol is biosynthesized by all animal cells. Beyond its metabolic role in steroidogenesis, it is enriched in the plasma membrane where it has key structural and regulatory functions. Cholesterol is thus presumably important for post-injury axon regrowth, and this notion is supported by studies showing that impairment of local cholesterol reutilization impeded regeneration. However, several studies have also shown that statins, inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, are enhancers of axon regeneration, presumably acting through an attenuation of the mevalonate isoprenoid pathway and consequent reduction in protein prenylation. Several recent reports have now shown that cholesterol depletion, as well as inhibition of cholesterol synthesis per se, enhances axon regeneration. Here, I discussed these findings and propose some possible underlying mechanisms. The latter would include possible disruptions to axon growth inhibitor signaling by lipid raft-localized receptors, as well as other yet unclear neuronal survival signaling process enhanced by cholesterol lowering or depletion.

Impacts and Burden of Niemann pick Type-C: a patient and caregiver perspective

Background

Niemann-Pick disease type C (NPC) is a debilitating condition that impacts patients’ and caregivers’ quality of life (QOL) and reduces the patient’s life expectancy. Since there is little qualitative research from the perspective of patients and family caregivers, this study explored the impact of NPC on patients’ and caregivers’ daily lives to understand the burden of disease.

Results

A survey of caregivers for patients with NPC and adult patients with NPC (n = 49; patient age: 13 months–65 years) assessed NPC severity, importance of NPC symptoms, and how symptoms impacted patients’ and caregivers’ activities of daily living (ADLs) and health-related QOL (HRQOL). Follow-up interviews with a subset of survey participants (n = 28) explored the ranking of NPC symptom importance and impact on ADLs and HRQOL. Findings indicated that the most important manifestations of NPC were ambulation, swallowing, speech, fine motor skills, and cognition, which were those that had the most significant impact on ADLs and HRQOL. A wide range of ADLs were affected by NPC, mainly eating/drinking and the ability to perform daily tasks, including self-care, communicating, participating in school or work, and moving indoors as well as outside the home. Along with these impacts, there was an increased risk of experiencing dangerous or life-threatening situations leading to loss of patient independence and additional caregiver burden, often requiring changes in lifestyle such as giving up work. All aspects of patients’ and caregivers’ HRQOL were affected. Participants reported feelings of social isolation, loss of enjoyment in activities (patients), and feelings of sadness or worry (caregivers).

Conclusions

Ambulation, swallowing, speech, fine motor skills, and cognition are important manifestations of NPC. ADLs and HRQOL were impaired in the majority of patients as well as their caregivers. The findings were independent of current age, age of onset of symptoms, and level of NPC disease-related disability; however, the impact increased at higher levels of disease disability. Knowing the impact of NPC on patients and caregivers is important for understanding the lived experience of NPC and for identifying potential areas of support.

Cyclodextrins Exert a Ligand-like Current Inhibitory Effect on the KV1.3 Ion Channel Independent of Membrane Cholesterol Extraction

Cyclodextrins (CDs) are cyclic oligosaccharides capable of forming water-soluble complexes with a variety of otherwise poorly soluble molecules including cholesterol and different drugs. Consistently, CDs are widely used in research and clinical practice to deplete cholesterol from cellular membranes or to increase solubility and bioavailability of different pharmaceuticals at local concentrations in the millimolar range. Effects of CDs exerted on cellular functions are generally thought to originate from reductions in cholesterol levels. Potential direct, ligand-like CD effects are largely neglected in spite of several recent studies reporting direct interaction between CDs and proteins including AMP-activated protein kinase, β-amyloid peptides, and α-synuclein. In this study, by using patch-clamp technique, time-resolved quantitation of cholesterol levels and biophysical parameters and applying cholesterol-extracting and non-cholesterol-extracting CDs at 1 and 5 mM concentrations, we provide evidence for a previously unexplored ligand-like, cholesterol-independent current inhibitory effect of CDs on K_V1.3, a prototypical voltage-gated potassium channel with pathophysiological relevance in various autoimmune and neurodegenerative disorders. Our findings propose that potential direct CD effects on K_V channels should be taken into consideration when interpreting functional consequences of CD treatments in both research and clinical practice. Furthermore, current-blocking effects of CDs on K_V channels at therapeutically relevant concentrations might contribute to additional beneficial or adverse effects during their therapeutic applications.

Cerebellar Long Noncoding RNA Expression Profile in a Niemann-Pick C Disease Mouse Model

Niemann-Pick type C (NP-C) disease is a neurodegenerative lysosomal storage disorder primarily caused by mutations in NPC1. However, its pathogenesis remains poorly understood. While mounting evidence has demonstrated the involvement of long noncoding RNAs (lncRNAs) in the pathogenesis of neurodegenerative disorders, the lncRNA expression profile in NP-C has not been determined. Here, we used RNA-seq analysis to determine lncRNA and mRNA expression profiles of the cerebella of NPC1^−/− mice. We found that 272 lncRNAs and 856 mRNAs were significantly dysregulated in NPC1^−/− mice relative to controls (≥ 2.0-fold, p < 0.05). Quantitative real-time PCR (qRT‐PCR) was utilized to validate the expression of selected lncRNAs and mRNAs. Next, a lncRNA-mRNA coexpression network was employed to examine the potential roles of the differentially expressed (DE) lncRNAs. Functional analysis revealed that mRNAs coexpressed with lncRNAs are mainly linked to immune system–related processes and neuroinflammation. Moreover, knockdown of the lncRNA H19 ameliorated changes in ROS levels and cell viability and suppressed the lipopolysaccharide (LPS)–induced inflammatory response in vitro. Our findings indicate that dysregulated lncRNA expression patterns are associated with NP-C pathogenesis and offer insight into the development of novel therapeutics based on lncRNAs.

Myelin Defects in Niemann-Pick Type C Disease: Mechanisms and Possible Therapeutic Perspectives

Niemann–Pick type C (NPC) disease is a wide-spectrum clinical condition classified as a neurovisceral disorder affecting mainly the liver and the brain. It is caused by mutations in one of two genes, NPC1 and NPC2, coding for proteins located in the lysosomes. NPC proteins are deputed to transport cholesterol within lysosomes or between late endosome/lysosome systems and other cellular compartments, such as the endoplasmic reticulum and plasma membrane. The first trait of NPC is the accumulation of unesterified cholesterol and other lipids, like sphingosine and glycosphingolipids, in the late endosomal and lysosomal compartments, which causes the blockade of autophagic flux and the impairment of mitochondrial functions. In the brain, the main consequences of NPC are cerebellar neurodegeneration, neuroinflammation, and myelin defects. This review will focus on myelin defects and the pivotal importance of cholesterol for myelination and will offer an overview of the molecular targets and the pharmacological strategies so far proposed, or an object of clinical trials for NPC. Finally, it will summarize recent data on a new and promising pharmacological perspective involving A_2A adenosine receptor stimulation in genetic and pharmacological NPC dysmyelination models.

Glial contribution to cyclodextrin-mediated reversal of cholesterol accumulation in murine NPC1-deficient neurons in vivo

Niemann-Pick type C disease is a rare and fatal lysosomal storage disorder presenting severe neurovisceral symptoms. Disease-causing mutations in genes encoding either NPC1 or NPC2 protein provoke accumulation of cholesterol and other lipids in specific structures of the endosomal-lysosomal system and degeneration of specific cells, notably neurons in the central nervous system (CNS). 2-hydroxypropyl-beta-cyclodextrin (CD) emerged as potential therapeutic approach based on animal studies and clinical data, but the mechanism of action in neurons has remained unclear. To address this topic in vivo, we took advantage of the retina as highly accessible part of the CNS and intravitreal injections as mode of drug administration. Coupling CD to gold nanoparticles allowed us to trace its intracellular location. We report that CD enters the endosomal-lysosomal system of neurons in vivo and enables the release of lipid-laden lamellar inclusions, which are then removed from the extracellular space by specific types of glial cells. Our data suggest that CD induces a concerted action of neurons and glial cells to restore lipid homeostasis in the central nervous system.

Neuroinflammation: An Integrating Overview of Reactive-Neuroimmune Cell Interactions in Health and Disease

The concept of central nervous system (CNS) inflammation has evolved over the last decades. Neuroinflammation is the response of reactive CNS components to altered homeostasis, regardless of the cause to be endogenous or exogenous. Neurological diseases, whether traumatic, neoplastic, ischemic, metabolic, toxic, infectious, autoimmune, developmental, or degenerative, involve direct and indirect immune-related neuroinflammation. Brain infiltrates of the innate and adaptive immune system cells appear in response to an infective or otherwise noxious agent and produce inflammatory mediators. Mediators of inflammation include local and recruited cells and signals. Processes derived from extrinsic and intrinsic CNS diseases also elicit the CNS inflammatory response. A deeper understanding of immune-related inflammation in health and disease is necessary to find potential therapeutic targets for preventing or reducing CNS damage. This review is aimed at discussing the innate and adaptive immune system functions and their roles in regulating brain cell responses in disease and homeostasis maintenance.

Life in the lumen: The multivesicular endosome

The late endosomes/endo‐lysosomes of vertebrates contain an atypical phospholipid, lysobisphosphatidic acid (LBPA) (also termed bis[monoacylglycero]phosphate [BMP]), which is not detected elsewhere in the cell. LBPA is abundant in the membrane system present in the lumen of this compartment, including intralumenal vesicles (ILVs). In this review, the current knowledge on LBPA and LBPA‐containing membranes will be summarized, and their role in the control of endosomal cholesterol will be outlined. Some speculations will also be made on how this system may be overwhelmed in the cholesterol storage disorder Niemann‐Pick C. Then, the roles of intralumenal membranes in endo‐lysosomal dynamics and functions will be discussed in broader terms. Likewise, the mechanisms that drive the biogenesis of intralumenal membranes, including ESCRTs, will also be discussed, as well as their diverse composition and fate, including degradation in lysosomes and secretion as exosomes. This review will also discuss how intralumenal membranes are hijacked by pathogenic agents during intoxication and infection, and what is the biochemical composition and function of the intra‐endosomal lumenal milieu. Finally, this review will allude to the size limitations imposed on intralumenal vesicle functions and speculate on the possible role of LBPA as calcium chelator in the acidic calcium stores of endo‐lysosomes.

Inhibition of Soluble Epoxide Hydrolase Ameliorates Phenotype and Cognitive Abilities in a Murine Model of Niemann Pick Type C Disease

Niemann-Pick type C (NPC) disease is a rare autosomal recessive inherited childhood neurodegenerative disease characterized by the accumulation of cholesterol and glycosphingolipids, involving the autophagy-lysosome system. Inhibition of soluble epoxide hydrolase (sEH), an enzyme that metabolizes epoxy fatty acids (EpFAs) to 12-diols, exerts beneficial effects in modulating inflammation and autophagy, critical features of the NPC disease. This study aims to evaluate the effects of UB-EV-52, an sEH inhibitor (sEHi), in an NPC mouse model (Npc) by administering it for 4 weeks (5 mg/kg/day). Behavioral and cognitive tests (open-field test (OF)), elevated plus maze (EPM), novel object recognition test (NORT) and object location test (OLT) demonstrated that the treatment produced an improvement in short- and long-term memory as well as in spatial memory. Furthermore, UB-EV-52 treatment increased body weight and lifespan by 25% and reduced gene expression of the inflammatory markers (i.e., Il-1β and Mcp1) and enhanced oxidative stress (OS) markers (iNOS and Hmox1) in the treated Npc mice group. As for autophagic markers, surprisingly, we found significantly reduced levels of LC3B-II/LC3B-I ratio and significantly reduced brain protein levels of lysosomal-associated membrane protein-1 (LAMP-1) in treated Npc mice group compared to untreated ones in hippocampal tissue. Lipid profile analysis showed a significant reduction of lipid storage in the liver and some slight changes in homogenated brain tissue in the treated NPC mice compared to the untreated groups. Therefore, our results suggest that pharmacological inhibition of sEH ameliorates most of the characteristic features of NPC mice, demonstrating that sEH can be considered a potential therapeutic target for this disease.

Loss of NPC1 enhances phagocytic uptake and impairs lipid trafficking in microglia

Niemann-Pick type C disease is a rare neurodegenerative disorder mainly caused by mutations in NPC1, resulting in abnormal late endosomal/lysosomal lipid storage. Although microgliosis is a prominent pathological feature, direct consequences of NPC1 loss on microglial function remain not fully characterized. We discovered pathological proteomic signatures and phenotypes in NPC1-deficient murine models and demonstrate a cell autonomous function of NPC1 in microglia. Loss of NPC1 triggers enhanced phagocytic uptake and impaired myelin turnover in microglia that precede neuronal death. Npc1^−/− microglia feature a striking accumulation of multivesicular bodies and impaired trafficking of lipids to lysosomes while lysosomal degradation function remains preserved. Molecular and functional defects were also detected in blood-derived macrophages of NPC patients that provide a potential tool for monitoring disease. Our study underscores an essential cell autonomous role for NPC1 in immune cells and implies microglial therapeutic potential.

Niemann-Pick type C disease is a rare childhood neurodegenerative disorder predominantly caused by mutations in NPC1, resulting in abnormal late endosomal and lysosomal defects. Here the authors show that NPC1 disruption largely impairs microglial function.

Validation of the 5-domain Niemann-Pick type C Clinical Severity Scale

Background

Niemann-Pick disease type C (NPC) is an ultra-rare, progressive, genetic disease leading to impaired lysosomal function and neurodegeneration causing serious morbidity and shortened life expectancy.

The Niemann-Pick type C Clinical Severity Scale (NPCCSS) is a 17 domain, disease-specific, clinician-reported outcome measure of disease severity and progression. An abbreviated 5-domain NPCCSS scale has been developed (measuring Ambulation, Swallow, Cognition, Speech, and Fine Motor Skills) and the scale reliability has been established. Additional psychometric properties and meaningful change of the scale need, however, to be assessed.

Methods

Mixed method studies were conducted to ascertain which NPCCSS domains were most important, as well as to explore meaningful change: 1) surveys in caregivers/patients (n = 49) and 2) interviews with clinicians (n = 5) as well as caregivers/patients (n = 28). Clinical trial data (n = 43) assessed construct validity and meaningful change through an anchor-based approach.

Results

Domains identified as most important by clinicians, caregivers, and patients (independent of current age, age of onset, and disease severity) were Ambulation, Swallow, Cognition, Speech, and Fine Motor Skills, indicating content validity of the 5-domain NPCCSS.

Criterion validity was shown with the 5-domain NPCCSS being highly correlated with the 17-item NPCCSS total score (excluding hearing domains), r² = 0.97. Convergent validity was demonstrated against the 9 Hole Peg Test, r² = 0.65 (n = 31 patients), and the Scale for Assessment and Rating of Ataxia (SARA), r² = 0.86 (n = 49 patients). Any change was seen as meaningful by patients/caregivers across domains. Meaningful change using trial data and interviews with NPC experts (n = 5) and patients/caregivers (n = 28) suggested that a 1-category change on a domain is equivalent to 1-point change or greater in the 5-domain NPCCSS total score.

Conclusions

Qualitative and quantitative data support content and construct validity of the 5-domain NPCCSS score as a valid endpoint in NPC trials. A 1-category change on any domain is equivalent to 1-point change or greater in the 5 domain NPCCSS total score, representing a clinically meaningful transition and reflecting loss of complex function and increased disability.

Trial registration NCT02612129. Registered 23 November 2015, https://clinicaltrials.gov/ct2/show/NCT02612129

Lack of Annexin A6 Exacerbates Liver Dysfunction and Reduces Lifespan of Niemann-Pick Type C Protein-Deficient Mice

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by cholesterol accumulation caused by loss-of-function mutations in the Npc1 gene. NPC disease primarily affects the brain, causing neuronal damage and affecting motor coordination. In addition, considerable liver malfunction in NPC disease is common. Recently, we found that the depletion of annexin A6 (ANXA6), which is most abundant in the liver and involved in cholesterol transport, ameliorated cholesterol accumulation in Npc1 mutant cells. To evaluate the potential contribution of ANXA6 in the progression of NPC disease, double-knockout mice (Npc1^-/-/Anxa6^-/-) were generated and examined for lifespan, neurologic and hepatic functions, as well as liver histology and ultrastructure. Interestingly, lack of ANXA6 in NPC1-deficient animals did not prevent the cerebellar degeneration phenotype, but further deteriorated their compromised hepatic functions and reduced their lifespan. Moreover, livers of Npc1^-/-/Anxa6^-/- mice contained a significantly elevated number of foam cells congesting the sinusoidal space, a feature commonly associated with inflammation. We hypothesize that ANXA6 deficiency in Npc1^-/- mice not only does not reverse neurologic and motor dysfunction, but further worsens overall liver function, exacerbating hepatic failure in NPC disease.

Delineation of metabolic responses of Npc1-/-nih mice lacking the cholesterol-esterifying enzyme SOAT2 to acute treatment with 2-hydroxypropyl-β-cyclodextrin

Lipids present in lipoproteins cleared from the circulation are processed sequentially by three major proteins within the late endosomal/lysosomal (E/L) compartment of all cells: lysosomal acid lipase (LAL), Niemann-Pick (NPC) C2 and NPC1. When all three of these proteins are functioning normally, unesterified cholesterol (UC) exits the E/L compartment and is used in plasma membrane maintenance and various pathways in the endoplasmic reticulum including esterification by sterol O-acyltransferase 2 (SOAT2) or SOAT1 depending partly on cell type. Mutations in either NPC2 or NPC1 result in continual entrapment of UC and glycosphingolipids leading to neurodegeneration, pulmonary dysfunction, splenomegaly and liver damage. To date, the most effective agent for promoting release of entrapped UC in nearly all organs of NPC1-deficient mice and cats is 2-hydroxypropyl-β-cyclodextrin (2HPβCD). The cytotoxic nature of the liberated UC triggers various defenses including suppression of sterol synthesis and increased esterification. The present studies, using the Npc1-/-nih mouse model, measured the comparative quantitative importance of these two responses in the liver versus the spleen of Npc1-/-: Soat2+/+ and Npc1-/-: Soat2-/- mice in the 24 h following a single acute treatment with 2HPβCD. In the liver but not the spleen of both types of mice suppression of synthesis alone or in combination with increased esterification provided the major defense against the rise in unsequestered cellular UC content. These findings have implications for systemic 2HPβCD treatment in NPC1 patients in view of the purportedly low levels of SOAT2 activity in human liver.

Understanding and Treating Niemann-Pick Type C Disease: Models Matter

Biomedical research aims to understand the molecular mechanisms causing human diseases and to develop curative therapies. So far, these goals have been achieved for a small fraction of diseases, limiting factors being the availability, validity, and use of experimental models. Niemann–Pick type C (NPC) is a prime example for a disease that lacks a curative therapy despite substantial breakthroughs. This rare, fatal, and autosomal-recessive disorder is caused by defects in NPC1 or NPC2. These ubiquitously expressed proteins help cholesterol exit from the endosomal–lysosomal system. The dysfunction of either causes an aberrant accumulation of lipids with patients presenting a large range of disease onset, neurovisceral symptoms, and life span. Here, we note general aspects of experimental models, we describe the line-up used for NPC-related research and therapy development, and we provide an outlook on future topics.

Clinical disease progression and biomarkers in Niemann-Pick disease type C: a prospective cohort study

Background

Niemann–Pick disease type C (NPC) is a rare, progressive, neurodegenerative disease associated with neurovisceral manifestations resulting from lysosomal dysfunction and aberrant lipid accumulation. A multicentre, prospective observational study (Clinical Trials.gov ID: NCT02435030) of individuals with genetically confirmed NPC1 or NPC2 receiving routine clinical care was conducted, to prospectively characterize and measure NPC disease progression and to investigate potential NPC-related biomarkers versus healthy individuals. Progression was measured using the abbreviated 5-domain NPC Clinical Severity Scale (NPCCSS), 17-domain NPCCSS and NPC clinical database (NPC-cdb) score. Cholesterol esterification and heat shock protein 70 (HSP70) levels were assessed from peripheral blood mononuclear cells (PBMCs), cholestane-3β,5α-,6β-triol (cholestane-triol) from serum, and unesterified cholesterol from both PBMCs and skin biopsy samples. The inter- and intra-rater reliability of the 5-domain NPCCSS was assessed by 13 expert clinicians’ rating of four participants via video recordings, repeated after ≥ 3 weeks. Intraclass correlation coefficients (ICCs) were calculated.

Results

Of the 36 individuals with NPC (2–18 years) enrolled, 31 (86.1%) completed the 6–14-month observation period; 30/36 (83.3%) were receiving miglustat as part of routine clinical care. A mean (± SD) increase in 5-domain NPCCSS scores of 1.4 (± 2.9) was observed, corresponding to an annualized progression rate of 1.5. On the 17-domain NPCCSS, a mean (± SD) progression of 2.7 (± 4.0) was reported. Compared with healthy individuals, the NPC population had significantly lower levels of cholesterol esterification (p < 0.0001), HSP70 (p < 0.0001) and skin unesterified cholesterol (p = 0.0006). Cholestane-triol levels were significantly higher in individuals with NPC versus healthy individuals (p = 0.008) and correlated with the 5-domain NPCCSS (Spearman’s correlation coefficient = 0.265, p = 0.0411). The 5-domain NPCCSS showed high ICC agreement in inter-rater reliability (ICC = 0.995) and intra-rater reliability (ICC = 0.937).

Conclusions

Progression rates observed were consistent with other reports on disease progression in NPC. The 5-domain NPCCSS reliability study supports its use as an abbreviated alternative to the 17-domain NPCCSS that focuses on the most relevant domains of the disease. The data support the use of cholestane-triol as a disease monitoring biomarker and the novel methods of measuring unesterified cholesterol could be applicable to support NPC diagnosis. Levels of HSP70 in individuals with NPC were significantly decreased compared with healthy individuals.

Trial registration

CT-ORZY-NPC-001: ClincalTrials.gov NCT02435030, Registered 6 May 2015, https://clinicaltrials.gov/ct2/show/NCT02435030; EudraCT 2014–005,194-37, Registered 28 April 2015, https://www.clinicaltrialsregister.eu/ctr-search/trial/2014-005194-37/DE. OR-REL-NPC-01: Unregistered.

Investigating the Mechanism of Cyclodextrins in the Treatment of Niemann-Pick Disease Type C Using Crosslinked 2-Hydroxypropyl-β-cyclodextrin

Niemann-Pick disease type C (NPC) is a severe disorder that is characterized by intracellular transport abnormalities leading to cytoplasmic accumulation of lipids such as cholesterol and sphingolipids. The compound 2-hydroxypropyl-β-cyclodextrin (HPβCD) has high cholesterol complexation capacity and is currently under clinical investigation for the NPC treatment. However, due to its short blood half-life, high doses are required to produce a therapeutic effect. In this work, stable polymerized HPβCD is generated to investigate their in vitro mechanisms of action and in vivo effects. Crosslinked CDs (8-312 kDa) display a ninefold greater cholesterol complexation capacity than monomeric HPβCD but are taken up to a lower extent, resulting in an overall comparable in vitro effect. In vivo, the 19.3 kDa HPβCD exhibits a longer half-life than the monomeric HPβCD but it does not increase the life span of Npc1 mice, possibly due to reduced brain penetration. This is circumvented by the application of magnetic resonance imaging-guided low intensity-pulsed focused ultrasound (MRIg-FUS), which increases the brain penetration of the CD. In conclusion, stable polymerized HPβCDs can elucidate CDs' mechanism of action while the use of MRIg-FUS warrants further investigation, as it may be key to harnessing CDs full therapeutic potential in the NPC treatment.

Lipophagy and Lipolysis Status in Lipid Storage and Lipid Metabolism Diseases

This review discusses how lipophagy and cytosolic lipolysis degrade cellular lipids, as well as how these pathway ys communicate, how they affect lipid metabolism and energy homeostasis in cells and how their dysfunction affects the pathogenesis of lipid storage and lipid metabolism diseases. Answers to these questions will likely uncover novel strategies for the treatment of aforementioned human diseases, but, above all, will avoid destructive effects of high concentrations of lipids-referred to as lipotoxicity-resulting in cellular dysfunction and cell death.

Clinical and Molecular Features of Early Infantile Niemann Pick Type C Disease

Niemann Pick disease type C (NPC) is a neurovisceral disorder due to mutations in NPC1 or NPC2. This review focuses on poorly characterized clinical and molecular features of early infantile form of NPC (EIF) and identified 89 cases caused by NPC1 (NPC1) and 16 by NPC2 (NPC2) mutations. Extra-neuronal features were common; visceromegaly reported in 80/89 NPC1 and in 15/16 NPC2, prolonged jaundice in 30/89 NPC1 and 7/16 NPC2. Early lung involvement was present in 12/16 NPC2 cases. Median age of neurological onset was 12 (0-24) and 7.5 (0-24) months in NPC1 and NPC2 groups, respectively. Developmental delay and hypotonia were the commonest first detected neurological symptoms reported in 39/89 and 18/89 NPC1, and in 8/16 and 10/16 NPC2, respectively. Additional neurological symptoms included vertical supranuclear gaze palsy, dysarthria, cataplexy, dysphagia, seizures, dystonia, and spasticity. The following mutations in homozygous state conferred EIF: deletion of exon 1+promoter, c.3578_3591 + 9del, c.385delT, p.C63fsX75, IVS21-2delATGC, c. 2740T>A (p.C914S), c.3584G>T (p.G1195V), c.3478-6T>A, c.960_961dup (p.A321Gfs*16) in NPC1 and c.434T>A (p.V145E), c.199T>C (p.S67P), c.133C>T (p.Q45X), c.141C>A (p.C47X) in NPC2. This comprehensive analysis of the EIF type of NPC will benefit clinical patient management, genetic counselling, and assist design of novel therapy trials.

Potential COVID-19 therapeutics from a rare disease: weaponizing lipid dysregulation to combat viral infectivity

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus (SARS-CoV)-2 has resulted in the death of more than 328,000 persons worldwide in the first 5 months of 2020. Herculean efforts to rapidly design and produce vaccines and other antiviral interventions are ongoing. However, newly evolving viral mutations, the prospect of only temporary immunity, and a long path to regulatory approval pose significant challenges and call for a common, readily available, and inexpensive treatment. Strategic drug repurposing combined with rapid testing of established molecular targets could provide a pause in disease progression. SARS-CoV-2 shares extensive structural and functional conservation with SARS-CoV-1, including engagement of the same host cell receptor (angiotensin-converting enzyme 2) localized in cholesterol-rich microdomains. These lipid-enveloped viruses encounter the endosomal/lysosomal host compartment in a critical step of infection and maturation. Niemann-Pick type C (NP-C) disease is a rare monogenic neurodegenerative disease caused by deficient efflux of lipids from the late endosome/lysosome (LE/L). The NP-C disease-causing gene (NPC1) has been strongly associated with viral infection, both as a filovirus receptor (e.g., Ebola) and through LE/L lipid trafficking. This suggests that NPC1 inhibitors or NP-C disease mimetics could serve as anti-SARS-CoV-2 agents. Fortunately, there are such clinically approved molecules that elicit antiviral activity in preclinical studies, without causing NP-C disease. Inhibition of NPC1 may impair viral SARS-CoV-2 infectivity via several lipid-dependent mechanisms, which disturb the microenvironment optimum for viral infectivity. We suggest that known mechanistic information on NPC1 could be utilized to identify existing and future drugs to treat COVID-19.

Regulation of autophagy by inhibitory CSPG interactions with receptor PTPσ and its impact on plasticity and regeneration after spinal cord injury

Chondroitin sulfate proteoglycans (CSPGs), extracellular matrix molecules that increase dramatically following a variety of CNS injuries or diseases, have long been known for their potent capacity to curtail cell migrations as well as axon regeneration and sprouting. The inhibition can be conferred through binding to their major cognate receptor, Protein Tyrosine Phosphatase Sigma (PTPσ). However, the precise mechanisms downstream of receptor binding that mediate growth inhibition have remained elusive. Recently, CSPGs/PTPσ interactions were found to regulate autophagic flux at the axon growth cone by dampening the autophagosome-lysosomal fusion step. Because of the intense interest in autophagic phenomena in the regulation of a wide variety of critical cellular functions, we summarize here what is currently known about dysregulation of autophagy following spinal cord injury, and highlight this critical new mechanism underlying axon regeneration failure. Furthermore, we review how CSPGs/PTPσ interactions influence plasticity through autophagic regulation and how PTPσ serves as a switch to execute either axon outgrowth or synaptogenesis. This has exciting implications for the role CSPGs play not only in axon regeneration failure after spinal cord injury, but also in neurodegenerative diseases where, again, inhibitory CSPGs are upregulated.

Iron chelation by deferiprone does not rescue the Niemann-Pick Disease Type C1 mouse model

Niemann-Pick Disease Type C (NP-C) is a fatal lysosomal storage disorder with progressive neurodegeneration. In addition to the characteristic cholesterol and lipid overload phenotype, we previously found that altered metal homeostasis is also a pathological feature. Increased brain iron in the Npc1^-/- mouse model of NP-C may potentially contribute to neurodegeneration, similar to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Deferiprone (DFP) is a brain penetrating iron chelator that has demonstrated effectiveness in preventing neurological deterioration in Parkinson's disease clinical trials. Therefore, we hypothesized that DFP treatment, targeting brain iron overload, may have therapeutic benefits for NP-C. Npc1^-/- mice were assigned to four experimental groups: (1) pre-symptomatic (P15) + 75 mg/kg DFP; (2) pre-symptomatic (P15) + 150 mg/kg DFP; (3) symptomatic (P49) + 75 mg/kg DFP; (4) symptomatic (P49) + 150 mg/kg DFP. Our study found that in Npc1^-/- mice, DFP treatment did not offer any improvement over the expected disease trajectory and median lifespan. Moreover, earlier treatment and higher dose of DFP resulted in adverse effects on body weight and onset of ataxia. The outcome of our study indicated that, despite increased brain iron, Npc1^-/- mice were vulnerable to pharmacological iron depletion, especially in early life. Therefore, based on the current model, iron chelation therapy is not a suitable treatment option for NP-C.

Addressing neurodegeneration in lysosomal storage disorders: Advances in Niemann Pick diseases

Most lysosomal storage disorders (LSDs) cause progressive neurodegeneration leading to early death. While the genetic defects that cause these disorders impact all cells of the body, neurons are particularly affected. This vulnerability may be explained by neuronal cells' critical dependence on the lysosomal degradative capacity, as they cannot use division to eliminate their waste. However, mounting evidence supports the extension of storage beyond lysosomes to other cellular compartments (mitochondria, plasma membrane and synapses) as a key event in pathogenesis. Impaired energy supply, oxidative stress, calcium imbalance, synaptic failure and glial alterations may all contribute to neuronal death and thus could be suitable therapeutic targets for these disorders. Here we review the pathological mechanisms underlying neurodegeneration in Niemann Pick diseases and therapeutic strategies developed in animal models and patients suffering from these devastating disorders. This article is part of the special issue entitled 'The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders'.